US20120172655A1 - Impeller housing for percutaneous heart pump - Google Patents

Abstract

Disclosed herein are heart pumps that include a catheter assembly and that can be applied percutaneously. Some embodiments include a locking device that prevents components of the catheter assembly from being separated when in use. The catheter assembly can include an expandable tip. In some embodiments, the catheter assembly includes a housing having a wall structure, a portion of which can have a bulbuous shape or can be deformable. In other embodiments, the housing can be configured to reduce fluttering or deflection of the housing and/or to maintain a gap between the housing and an impeller blade disposed therein.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims priority to U.S. Provisional Application Ser. No. 61/430,146 filed Jan. 5, 2011 entitled Impeller Housing For Percutaneous Heart Pump, which is hereby incorporated by reference herein for all purposes.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• This application is directed to heart pumps that can be applied percutaneously.
• 2. Description of the Related Art
• Heart disease is a major health problem that claims many lives per year. After a heart attack, only a small number of patients can be treated with medicines or other non-invasive treatment. However, a significant number of patients can recover from a heart attack or cardiogenic shock if provided with mechanical circulatory support.
• In a conventional approach, a blood pump having a fixed cross-section is surgically inserted a heart chamber, such as into the left ventricle of the heart and the aortic arch to assist the pumping function of the heart. Other known applications involve providing for pumping venous blood from the right ventricle to the pulmonary artery for support of the right side of the heart. The object of the surgically inserted pump is to reduce the load on the heart muscle for a period of time, which may be as long as a week, allowing the affected heart muscle to recover and heal. Surgical insertion, however, can cause additional serious stresses in heart failure patients.
• Percutaneous insertion of a left ventricular assist device (“LVAD”), a right ventricular assist device (“RVAD”) or in some cases a system for both sides of the heart (sometimes called biVAD) therefore is desired. Conventional fixed cross-section ventricular assist devices designed to provide near full heart flow rate are too large to be advanced percutaneously, e.g., through the femoral artery. There is an urgent need for a pumping device that can be inserted percutaneous and also provide full cardiac rate flows of the left, right, or both the left and right sides of the heart when called for.
SUMMARY OF THE INVENTION
• A catheter assembly for a heart pump is provided that includes an elongate tubular member and a hub coupled with a proximal end of the elongate tubular member. Optionally, the hub has an increasing outer profile along its length. The catheter assembly includes a plurality of structural members forming a distal portion of an impeller housing and a locking device disposed between the structural members and the hub. The locking device is configured to prevent the elongate tubular member from being separated from the structural members when the catheter assembly is in use.
• In another embodiment, an impeller assembly for a heart pump is provided that includes an impeller housing, an impeller assembly, and a stiffening member. The impeller housing comprises a fixed profile proximal portion, an expandable portion, and a plurality of struts extending therebetween. The struts have a proximal end coupled with the proximal portion of the impeller housing and a distal end coupled with the expandable portion of the impeller housing and movable with the expandable portion of the impeller housing from a low profile configuration to a higher profile configuration. The an impeller assembly includes an impeller shaft journaled for rotation within the impeller housing and at least one impeller blade supported by the impeller shaft for rotation within the expandable portion of the impeller housing. The stiffening member is coupled with the proximal portion of the impeller housing and with the expandable portion of the impeller housing. The stiffening member is configured to limit deflection of at least one of the impeller shaft, the impeller blade or the impeller housing from a desired position relative to a central axis of the impeller assembly.
• In another embodiment, a catheter assembly for a heart pump is provided. The catheter assembly includes an impeller shaft and an impeller blade extending from the impeller shaft and a housing in which the impeller shaft is journaled for rotation. The housing has an elongate wall structure disposed circumferentially about the impeller blade. The elongate wall structure extends distally and proximally of the impeller blade. The wall structure is sufficiently deformable to be displaced by ambient conditions during operation of the impeller assembly within a patient.
• In some embodiments impeller assembly is modified such that the wall structure is made stiffer to control deflections of the wall of the housing at the location of the impeller blade or blades.
• In some variations the stiffness of the housing varies along the length thereof such that more deflection or deformation is provided for proximal, distal or proximal and distal of the region of the impeller blade or blades.
• In some variations the stiffness of the housing is increased such that little if any deflection of the wall is anticipated under normal operating conditions of a heart pump in which the impeller housing is incorporated. This arrangement may be useful where deflections during rotation of the impeller shaft and blade or blades are very tightly controlled in normal operational conditions.
• In another embodiment, a catheter assembly for a heart pump is provided. The catheter assembly includes an impeller shaft and an impeller blade extending from the impeller shaft and an impeller housing in which the impeller shaft is journaled for rotation. The housing includes an inlet, an outlet, and an elongate wall structure disposed circumferentially about the impeller blade. The housing extends distally and proximally of the impeller blade between the inlet and outlet. The wall structure adjacent to at least one of the inlet and the outlet is configured to maintain a bulbous shape when deployed.
• In another embodiment, an impeller assembly for a heart pump is provided that includes an impeller shaft and an impeller blade extending from the impeller shaft. The impeller assembly also includes a housing in which the impeller shaft is journaled for rotation. The housing comprising an impeller blade zone, an inlet zone, and an outlet zone, the impeller blade zone being elongate and having a substantially constant transverse size zone at least from proximal of the impeller blade to distal of the impeller blade. The impeller zone is disposed between the inlet zone and the outlet zone. At least one of the inlet zone and the outlet zone is configured to reduce fluttering of the housing when the heart pump is operating.
• In another embodiment, a catheter assembly for a heart pump is provided that includes an elongate tubular member, and an expandable housing disposed at the distal end of the elongate tubular member, and an expandable tip. The expandable housing is configured to house an impeller and to convey blood from an intake toward the impeller in use. The expandable tip is coupled with the distal end of the expandable housing. The expandable tip has a collapsed configuration in which a tapered profile is provided for facilitating advancement through an anatomical structure. The expandable tip has an expanded configuration for spacing the intake from the anatomy adjacent to where the pump operates.
• In another embodiment, a catheter assembly for a heart pump is disclosed that comprises an impeller shaft and an impeller blade extending from the impeller shaft. The catheter assembly further includes a housing in which the impeller shaft is journaled for rotation, the housing having an elongate wall structure disposed circumferentially about the impeller blade and extending distally and proximally thereof. A distal region of the wall structure can be configured to isolate a proximal region of the wall structure from deflection due to application of loads by the heart during operation of the impeller assembly within the patient.
• In another embodiment, a percutaneous heart pump is disclosed that comprises a catheter assembly having a proximal end, a distal end, and an elongate body disposed therebetween. The elongate body can be configured such that the distal end can be disposed inside heart chamber of a human patient while a proximal end is disposed outside the patient. The distal end can comprise an expandable housing being configured to be insertable into a peripheral vessel in a low profile configuration and to be expanded to a larger profile within the patient. The percutaneous heart pump can further include an impeller shaft and an impeller blade extending from the impeller shaft, the impeller shaft being journaled for rotation in the distal portion of the catheter assembly. The expandable housing can comprise an elongate wall structure disposed circumferentially about the impeller blade and extending distally and proximally thereof, the wall being configured to maintain a gap between the blade an inner surface of the wall structure within a selected range over a range of transverse loading corresponding to forces generated during systole and diastole of the heart.
• In another embodiment, a catheter assembly for a heart pump is disclosed. The catheter assembly can comprise an impeller shaft and an impeller blade extending from the impeller shaft. The catheter assembly can further include a housing in which the impeller shaft is journaled for rotation, and the housing can have an elongate wall structure, a portion of which is disposed circumferentially about the impeller blade and the impeller shaft. The wall structure can be configured to provide a first stiffness over the impeller blade and a second stiffness greater than the first stiffness at a location proximal of the impeller blade to reduce bending of the housing proximal of the blade.
BRIEF DESCRIPTION OF THE DRAWINGS
• A more complete appreciation of the subject matter of the present inventions and the various advantages thereof can be realized by reference to the following detailed description, in which reference is made to the accompanying drawings in which:
• FIG. 1 illustrates one embodiment of a heart pump configured for percutaneous application and operation;
• FIG. 1A is a plan view of one embodiment of a catheter assembly adapted to be used with the heart pump ofFIG. 1;
• FIG. 2 is a detail view of a distal portion of the catheter assembly illustrated inFIG. 1A;
• FIG. 3 is an exploded view of a portion of an impeller assembly of the catheter assembly ofFIG. 1A;
• FIG. 4A is a cross-sectional view of a distal portion of the catheter assembly, taken through thesection plane4A-4A shown inFIG. 2;
• FIG. 4B is a detail view of the distal portion of the catheter assembly, taken at4B-4B shown inFIG. 4A;
• FIG. 5 is a cross-sectional perspective view of a bearing assembly of the heart pump ofFIG. 1A;
• FIG. 6 is a cross-sectional view of a bearing housing of the bearing assembly ofFIG. 5;
• FIG. 7 is a perspective view of one embodiment of a catheter body that can be used to house a drive shaft and to convey an infusant to the bearing housing ofFIG. 5;
• FIGS. 7A-7C show variations of the catheter body ofFIG. 7;
• FIG. 8 illustrates a surface configuration of one embodiment of a bearing adapted to enhance or control flow of an infusant in the bearing assembly ofFIG. 5;
• FIG. 9 illustrates one embodiment of an impeller assembly;
• FIGS. 9A,9B-1,9B-2,10 and10A illustrate details of further embodiments of impeller blade;
• FIG. 11 is a cross-sectional view of a proximal portion of the catheter assembly, taken through the section plane11-11 onFIG. 1A.
• FIGS. 12,12A, and12B are cross-section views similar to that ofFIG. 11, illustrating an infusant outflow path;
• FIGS. 13A-13B illustrate side views of various embodiments of the flexible tip assembly.
• FIG. 14 is a perspective view of an embodiment of a flexible tip assembly that can be used in a heart pump;
• FIG. 15 is an exploded view of the flexible tip assembly ofFIGS. 13A-B;
• FIG. 16A illustrates another embodiment of a flexible tip assembly;
• FIG. 16 is a cross-sectional view of a portion of another embodiment of a flexible tip assembly in which a barrier structure is provided for separating components of an interlocking assembly from a lumen of the tip assembly;
• FIG. 17 is a cross-section view of a portion of another embodiment of a flexible tip assembly that is configured to resist detachment of components thereof due to opposed forced being applied at opposite ends of the flexible tip assembly;
• FIGS. 18A-18B illustrate another embodiment of a flexible tip assembly having an extended dilating structure;
• FIG. 19 is a perspective view of another embodiment of a flexible tip assembly;
• FIG. 19A is a perspective view of another embodiment of a flexible tip assembly;
• FIG. 20 is an exploded view of another embodiment of a flexible tip assembly;
• FIG. 21-21B illustrate embodiments of a portion of an impeller housing that is configured to be securely integrated into an insert molded hub of a flexible tip assembly;
• FIGS. 22-22B illustrate the relative position of an impeller blade and an inner surface of an impeller housing in a steady-state undeflected configuration;
• FIGS. 23-23B illustrate the relative position of an impeller blade and an inner surface of an impeller housing in a transient deflected configuration;
• FIGS. 24-25 illustrate embodiments of impeller housings that are configured to provide enhanced support to minimize deflections of the housing;
• FIG. 26 is a side elevational view of the distal end of an expandable cannula;
• FIGS. 27 and 28 are schematic side elevational view of the proximal end of an embodiment of an expandable cannula showing a diffuser arrangement; and
• FIG. 29 is a schematic side elevational view of the proximal end of an embodiment of an expandable cannula showing its relationship to an impeller hub diffuser;
• FIGS. 30 illustrate another embodiment of catheter assembly in which a dilating structure is integrated into an impeller housing;
• FIG. 31 show the catheter assembly ofFIG. 30 in an expanded configuration with a guidewire in position;
• FIG. 32 is a plan view of the catheter assembly ofFIG. 30 in an expanded configuration with the guidewire removed;
• FIG. 33 is a detailed view of the distal end of an impeller assembly showing details of an expandable tip;
• FIG. 34 show the catheter assembly ofFIG. 30 in position within the anatomy;
• FIG. 35 illustrates deflection of an impeller housing when a load is applied to a distal portion thereof;
• FIG. 36 illustrates a wall pattern in a flat configuration that is configured to isolate an impeller region of an impeller assembly from a load such as that illustrated inFIG. 35;
• FIG. 36A-D illustrate in greater detail various regions of the wall pattern inFIG. 36;
• FIG. 37A-B illustrates additional techniques for isolating an impeller region of an impeller housing from a load;
• FIGS. 38-40 illustrates further embodiments of wall patterns than can be incorporated into an impeller housing; and
• FIG. 41 illustrates another embodiment of a wall pattern than can be incorporated into an impeller housing to enhance the efficiency of an impeller disposed therein.
• More detailed descriptions of various embodiments of components for heart pumps useful to treat patients experiencing cardiac stress, including acute heart failure, are set forth below.
DETAILED DESCRIPTION
• This application is directed to aspects of heart pumps and components therefor that can be used to treat a patient experiencing cardiac stress, including acute heart failure. Major components of catheter-based pumps that can be applied to a patient percutaneously are described below in Section I. Section II describes distal end features application and performance of heart pumps. In particular, Section II(A) describes structures that facilitate advancement of a heart pump within the vasculature; Section II(B) describes impeller housing configurations that enhance fluid handling performance; and Section II(C) describes stabilizing structures for an impeller housing to control tip gap clearance. Section III illustrates techniques for reducing the complexity and crossing profile of a catheter assembly. Section IV describes features of an impeller assembly for improved performance when subject to operational loads during a heart pumping procedure. Section V discloses embodiments of an impeller housing for enhancing the flow of blood during operation of the impeller. Section VI illustrates methods for use in connection with specific structures of heart pumps.
• I. Heart Pump System Overview
• FIG. 1 illustrates one embodiment of aheart pump10 that includes acatheter assembly100 having aproximal end104 adapted to connect to amotor14 and a distal end108 (as shown inFIG. 1A) adapted to be inserted percutaneously into a patient. Themotor14 is connected by asignal line18 to acontrol module22 that provides power and/or control signals to themotor14. As discussed further below, theheart pump10 may have aninfusion system26 and apatient monitoring system30.
• Theinfusion system26 can provide a number of benefits to theheart pump10 which are discussed below. In one embodiment, theinfusion system26 includes a source ofinfusant34, afluid conduit38 extending from theinfusant source34 to theproximal end104 of thecatheter assembly100 and afluid conduit42 extending from the proximal end of thecatheter assembly100 to awaste container46. The flow of infusant to and from thecatheter assembly100 can be by any means, including a gravity system or one or more pumps. In the illustrated embodiment, theinfusant source34 includes anelevated container50, which may be saline or another infusant as discussed below. Flow from theelevated container50 can be regulated by apressure cuff54 to elevate the pressure of the fluid in thecontainer50 to increase flow or by apinch valve58 or by other means.
• Thepatient monitoring system30 can be used to monitor the operation of the patient and/or thepump10. For example, thepatient monitoring system30 can include auser interface60 coupled with a source ofdata64. Thedata source64 can include one or more patient conditions sensors, such aspressure sensors68 that are in pressure communication with the patient and/or operating components within the patient. In one embodiment, thepressure sensors68 fluidly communicate by aconduit72 that extends between the sensors and a proximal portion of thecatheter assembly100. Theconduit72 can include a plurality of separable segments and can include avalve76 to enable or disable the pressure communication to thesensors68.
• Theheart pump10 is adapted to provide an acute or other short-term treatment. A short-term treatment can be for less than a day or up to several days or weeks in some cases. With certain configurations thepump10 can be used for a month or more.
• FIG. 1A illustrates one embodiment of a catheter assembly to be used with theheart pump10. Animpeller assembly116 disposed at thedistal end108 is configured to pump blood proximally or distally through or along a portion of theheart pump10 to convey blood from one body cavity to another. Theimpeller assembly116 can be arranged to pump blood distally, such as in a right heart assist mode to move blood from the right ventricle to the pulmonary artery. Proximal flow is optimal for left heart support to move blood from the left ventricle to the aorta. As discussed below, theheart pump10 can be used to treat patients with acute heart failure, ST elevation myocardial infarction (STEMI), cardiac arrest, cardiac arrhythmia or other heart maladies. Theheart pump10 also can be used in connection with a surgical treatment to support the patient without providing full cardiovascular bypass. A patient could be supported on the device for longer term with proper controls and design.
• One feature that facilitates percutaneous insertion is providing thecatheter assembly100 with a low profile configuration. For example, thedistal end108 of thecatheter assembly100 can be configured to have about an 11 French (approximately 3.5 mm) size in a first configuration for insertion and an expanded configuration, such as up to about 21 French (approximately 7 mm) once in place in the body. The larger size facilitates greater flow rates by theimpeller assembly116 as discussed below.
• Thecatheter assembly100 is configured to enable thedistal end108 to reach a heart chamber after being inserted initially into a peripheral vessel. For example, thecatheter assembly100 can have a suitable length to reach the left ventricle and sufficient pushability and torquability to traverse the intervening vasculature. Thecatheter assembly100 may include amultilumen catheter body120 that is arranged to facilitate delivery and operation of an impeller of theimpeller assembly116. Further details concerning various embodiments of thecatheter body120 are illustrated inFIGS. 7-7B and described in more detail in U.S. Provisional Application No. 61/430,129, filed Jan. 5, 2010.
• A drive system is provided to drive an impeller within theimpeller assembly116. The drive system includes themotor14 and a drive controller, which can be integrated into thecontrol module22. Although themotor14 may be configured to be disposed outside the patient, some structures and assemblies described herein could be incorporated into a system in which a motor is miniaturized sufficiently to be inserted into the patient in use, including into the vasculature.
• A torque coupling system is provided for transferring torque from themotor14 to theimpeller assembly116. The torque coupling system is discussed further in U.S. Provisional Application No. 61/430,129, filed Jan. 5, 2010, but in general can include a mechanical or magnetic interface disposed between themotor14 and a drive assembly illustrated inFIG. 11 that is disposed at theproximal end104 of thecatheter assembly100. The drive assembly is coupled with a proximal end of anelongate drive shaft148 in one embodiment. Thedrive shaft148 extends between thedrive assembly146 and theimpeller assembly116. A distal portion of thedrive shaft148 is coupled with theimpeller assembly116 as illustrated below in connection with one embodiment illustrated inFIGS. 4A and 4B.FIG. 11 shows one manner of coupling the proximal end of thedrive shaft148 with thedrive assembly146.
• FIG. 1A shows aninfusion inflow assembly150 that can form a part of the infusion system26 (seeFIG. 1). The infusion in theassembly150 is provided adjacent theproximal end104 in one embodiment. Theinfusion system26 is configured to convey one or more fluids therein in connection with operation of theimpeller assembly116 or the conducting of the treatment. In one embodiment, an infusant, e.g., a medication or a lubricating fluid, such as saline or other beneficial medium, is conveyed distally along the pump, e.g., within thecatheter body120, toward operating components adjacent thedistal end108. The infusant can include lubrication fluids such as glucose or other biocompatible lubricants. Theinfusion inflow assembly150 includes acatheter body154 having a luer or othersuitable connector158 disposed at a proximal end thereof and an inflow port in fluid communication with one or more lumens within thecatheter assembly100. A lumen extending through thecatheter body154 is adapted to be fluidly coupled with a fluid source connected to theconnector158, to deliver the fluid into thecatheter assembly100 and through one or more flow paths as discussed below in connection withFIGS. 4A,4B, and7-7B.
• As discussed further below in connection withFIGS. 1A and 12, theinfusion system26 may also include an outlet positioned at a location that is outside the patient when theheart pump10 is in use, such that at least a portion of the infusant can be removed from theheart pump10 and the patient during or after the treatment. An infusant outlet assembly can include a lumen, e.g., within thefluid conduit42, that is fluidly coupled with an infusant return flow path in thecatheter body120 through a proximal end mechanical interface, for example.
• Thecatheter assembly100 can also include asheath assembly162 configured to constrain theimpeller assembly116 in a low profile configuration in a first state and to permit theimpeller assembly116 to expand to the enlarged configuration in a second state. Thesheath assembly162 has aproximal end166, adistal end170, and anelongate body174 extending therebetween. Theelongate body174 has a lumen extending between the proximal anddistal ends166,170. The lumen is configured to be slidably disposed over thecatheter body120. The arrangement permits thesheath assembly162 to be positioned between an advanced position corresponding to the low profile configuration and a retracted position corresponding to the enlarged configuration. In some embodiments, aluer102 or other suitable connector is in fluid communication with theproximal end166 of thesheath assembly162. Theluer102 can be configured to deliver fluids to thecatheter assembly100, such as priming fluid, infusant, or any other suitable fluid.
• FIG. 1A illustrates a retracted position, in which thedistal end170 of theelongate body174 is at a position proximal of theimpeller assembly116. In an advanced position, thedistal end170 of theelongate body174 is positioned distal of at least a portion of theimpeller assembly116. Thesheath assembly162 can be configured such that distal advancement of thedistal end170 over theimpeller assembly116 actuates theimpeller assembly116 to a low profile configuration, e.g., causing a change from the second state to the first state, as discussed above. Although shown inFIGS. 4A & 4B as a single layer, theelongate body174 can include a multilayer construction.
• FIGS. 1A and 2 show that ahousing202 is disposed at thedistal end108. Thehousing202 can be considered part of theimpeller assembly116 in that it houses an impeller and provides clearance between the impeller and the anatomy to prevent any harmful interactions therebetween. Thehousing202 and the impeller are also carefully integrated to maintain an appropriate flow regime, e.g., from distal to proximal within the housing.FIGS. 2,21A-B,22-23, and35A-41 show that in some embodiments thehousing202 includes a cage ormesh structure203 of filaments that extend axially along the housing and that wrap circumferentially around a central area of the housing in which an impeller of theimpeller assembly116 is disposed. Themesh structure203 can take any suitable form, such as being constructed to prevent kinking upon delivery or to control the spacing between a radially outer edge of an impeller and thehousing202, as discussed below. Thehousing202 forms a cannula through which blood flows during use of the system.
• If thecatheter assembly100 is used for left heart support, theheart pump10 andintake202A is provided at a distal end of thehousing202. The intake can be configured to remain open in operational conditions such as by having a shape that reduces or eliminate suck-down (e.g., suction causing the inlet to get stuck against wall surface) and to keep the inlet open. For example, as shown inFIGS. 31-33, various embodiments of the housing can be arranged with a bulbous shape (e.g., round, spherical, egg-shaped, oblate spheroidal, or any other shape that includes an enlarged portion having a non-linear curved outer surface) to prevent heart tissue from being drawn into the inlet to interfere with operation of theheart pump10. The shape also is useful to position the inlet from the wall.
• FIGS. 1A and 2 also show that thedistal end108 of thecatheter assembly100 includes anatraumatic tip182 disposed distal of theimpeller assembly116 in one embodiment. Theatraumatic tip182 can have an arcuate configuration such that interactions with a patient's internal tissues are controlled and do not cause trauma thereto. Thetip182 can take any suitable shape, which can vary depending on the degree of curvature of the tip. The tip is designed to be atraumatic so that after retraction of the guidewire, when the tip is left inside, for example, a ventricle, it cannot cause injury or trauma to the inner wall or endocardial surface of the ventricle resulting from motion of the ventricle.
• For example, theatraumatic tip182 can include a 180° bend, wherein the distal-most end of thetip182 is generally parallel to the non-arcuate portion of theatraumatic tip182, but extending in the opposite direction (e.g., a j-tip). In other embodiments, the distal-most end of thetip182 can be generally perpendicular to the non-arcuate portion of theatraumatic tip182, for example as illustrated inFIG. 19A, or at an angle between about 90° and about 180°, for example as illustrated inFIGS. 13A-B. In yet another embodiment, the distal-most end of thetip182 can include a 360° bend, wherein the distal-most end of thetip182 is generally parallel to the non-arcuate portion of the atraumatic tip, while extending in generally the same direction. In some embodiments, the arcuate portion of thetip182 can be coiled greater than 360°. The latter two embodiments may herein be referred to as a pigtail tip.
• FIGS. 3-12B illustrate additional features of the heart pump, as discussed in U.S. Provisional Application No. 61/430,129, filed Jan. 5, 2010 and as set forth in the appendix below.
• II. Heart Pump Distal End Configurations
• FIGS. 13-25 illustrate a variety of heart pumps embodiments that have advantageous distal or working end arrangements. These embodiments provide atraumatic distal tips and coupling of the same with distal portions of a catheter based heart pump. These embodiments also relate to particularly useful constructions of impeller housings that are able to collapse and expand as needed and also interact with blood cells in a minimally traumatic way. These embodiments also provide for secure engagement of an impeller housing with a proximal portion of the heart pump. Features of these embodiments can be interchanged and combined to arrive at different embodiments within the scope of this application.
A. Atraumatic Flexible Tip Structures
• As discussed above, theheart pump10 is configured as a catheter device that will be placed within the heart after being advanced through the vasculature. As such the distal portion of thepump100 should be as minimally traumatic as possible to the anatomy to be encountered. As discussed further below, the connection of the distal end of thehousing202 to thetip182 can be achieved by advantageous mechanical arrangements.
• 1. Interlock Configurations for Joining Flexible Tip to Impeller Housing
• FIGS. 13-19A illustrate a variety of embodiments for connecting theatraumatic tip182 to the distal end of theimpeller housing202.FIGS. 13A-13B illustrate another embodiment of theflexible tip assembly600 and how it can be attached to theimpeller housing202.FIG. 13A shows the distal end of an embodiment of thepump100, including theflexible tip assembly600, and thesheath assembly162 disposed proximally thereof. The embodiment ofFIG. 13A also shows ahub608 and aflexible member602.FIG. 13B showsflexible tip assembly600 anddistal members648 of theimpeller housing202.
• The embodiments ofFIGS. 14 and 15 include aflexible tip assembly600 having a locking arrangement for coupling theimpeller housing202 to theflexible member602. The locking arrangement can be configured to lock or secure a component of theimpeller housing202 between two components of thetip assembly600. These arrangements are sometimes referred to herein as an interface lock because in some cases they secure a distal structure of the housing at an interface between two separable structures. In this context, separable includes arrangements that can be assembled and disassembled rather than unitary arrangements.
• Theflexible tip assembly600 includes acore member604 and thehub608. Theflexible member602 can take any suitable form, but as illustrated inFIG. 15 may include aproximal portion612, adistal portion616, and anelongate body620 extending therebetween. Thedistal portion616 can take any suitable form, but may be made atraumatic, such as by including an arcuate portion as shown inFIG. 15. Theproximal portion612 may be configured to be coupled with a distal portion of thehub608. For example, theproximal portion612 can include a flared body that is adapted to be advanced onto thehub608.
• Thehub608 is configured to be disposed between theflexible member602 and thehousing202. Thehub608 may include adistal portion628 configured to be coupled with aproximal portion612 of theflexible member602. For example, anenlarged structure632 is disposed at the distal end of atubular body636 in one embodiment. Theenlarged structure632 can be a barb located at the distal end of thehub608. The proximal end of thehub608 can include arecess640 configured to receive thecore member604 therein.
• In one embodiment, thecore member604 and thehub608 are configured to secure therebetween the distal portion ofimpeller housing202.FIGS. 14 and 15 show that in one arrangement arecess644 is provided that is configured to receive a plurality ofdistal members648 of theimpeller housing202. Therecess644 can be provided with a profile with a shape similar to the shape of thedistal member648. Thecore member604 can be provided with a plurality of recesses dispose in an outer surface thereof. In one embodiment, each of therecesses644 is provided with a shape that matches a shape of the distal end of a corresponding one of themembers648.
• FIG. 14 illustrates one embodiment in which a T-shaped configuration is provided at the distal end of each of themembers648. Each of therecesses644 similarly is provided with a T-shaped configuration. In one arrangement therecess644 comprises a narrowproximal portion644A and a widedistal portion644B. The narrowproximal portion644A is configured to receive a slender length of themembers648 and the widedistal portion644B is configured to receive a distal-most end portion of themember648, which has a transverse width that is greater than the width of the slender length portion of themember648.
• In one embodiment thecore member604 and thehub608 are configured to be securely coupled together such that themembers648 of theimpeller housing202 are secured within theflexible tip assembly600.FIGS. 14 and 15 illustrate that in one arrangement, a plurality ofmembers648 is disposed about the perimeter of the distal portion of theimpeller housing202. In the illustrated embodiment, there are fourmembers648 at the distal end of thehousing202. Each of the fourmembers648 can be received within acorresponding recess644 of thecore member604. Thereafter thecore member604 along with the distal ends of the fourmembers648 disposed in therecesses644 can be inserted into therecess640 of thehub608.
• Securement of thecore member604 within thehub608 can be provided by any suitable technique. For example, as illustrated inFIGS. 14 and 15, a proximal portion of thecore member604 can be provided with anengagement feature660 configured to couple with acorresponding engagement feature664 disposed on thehub608. In the illustrated embodiment, theengagement feature660 disposed on thecore member604 comprises an arcuate protrusion extending away from aside surface668 of thecore member604. In the illustrated embodiment, thecorresponding engagement feature664 disposed on thehub608 includes anarcuate recess672 disposed within therecess640 of thehub608. Theengagement feature660 and recesses640,672 are more clearly shown onFIG. 16A, which is discussed in more detail below. In one embodiment, the arcuate protrusion that forms a least a part of theengagement feature660 can include a plurality of protrusions disposed about thecore member604. In various embodiments, protrusions are disposed at least on opposite sides of thecore member604. In one embodiment theengagement feature660 substantially surrounds the outer surface of thecore member604. In one embodiment, therecess672 comprises a circumferential channel surrounding therecess640 of thehub608.
• In one embodiment, a lumen676 (shown inFIG. 16A) extends through at least one of the components of theflexible tip assembly600. In some embodiments, thelumen676 extends from the proximal end of thecore member604 to the distal end of theflexible member602. Thelumen676 enables advancement of a guide wire through the pump, e.g., from the distal end of theelongate body620 into theimpeller housing202.
• FIG. 16A shows the proximal end of theelongate body602 advanced over theenlarged structure632 of thehub608. The proximal end of theelongate body602 is advanced into engagement with a distal-facingshoulder682 of thehub608. A length of thehub608 extending proximally from the distal-facingshoulder682 of the hub has a progressively larger outer perimeter, forming a dilatingstructure686. The dilatingstructure686 is disposed between the distal facingshoulder682 and a proximal-facingshoulder690 of thehub608. In the embodiment ofFIG. 16A the proximal facingshoulder690 is disposed proximal of the distal end of therecess640.
• FIGS. 13A and 16A shows that the proximal-facingshoulder690 is configured to abut against a distal end of thesheath assembly162. This configuration provides a generally smooth transition between the distal-facingshoulders682 and the proximal-facingshoulder690 as well as at the interface between thesheath assembly162 and the proximal-facingshoulder690. In one embodiment, a smooth transition is provided along the entire length from the distal facingshoulders682 to the proximal facing shoulders690.
• In some embodiments, asecurement device694 can be provided for coupling one or more of themembers648 to thecore member604 or within thehub608. In some variations, thesecurement device694 can be used to supplement the locking arrangement between thecore member604 and thehub608. In other embodiments, a mating arrangement is provided between the distal end of themembers648 and a corresponding recess in at least one of thecore member604 and thehub608. The mating arrangement can include therecess644 as discussed above. In another arrangement therecess644 can be eliminated and thesecurement device694 can be relied upon primarily for securing themember648. Thesecurement device694 can comprise an adhesive layer disposed over the distal end portion of one or more themembers648. Thesecurement device694 can extend distally from the distal end of one or more of themember648 onto the outer surface of thecore member604.
• FIG. 16 illustrates another embodiment that is similar to embodiment of FIGS.13A/B-16A except as set forth below.FIG. 16 illustrates aflexible tip assembly600A that is configured to provide a barrier to isolate certain components of theflexible tip assembly600 from thelumen676. For example, in some embodiments where asecondary securement device694 includes an adhesive, it may be advantageous to provide an additional degree of separation between the adhesive and any blood disposed near or within thelumen676.
• In one embodiment, a distal portion of therecess640 includes anannular protrusion710. Theannular protrusion710 can have a portion of thelumen676 extending therein. A well714 is disposed around theannular protrusion710 in one embodiment. The well714 can be configured as an annular recess extending distally of the proximal end of theannular protrusion710. The well714 is configured to receive at least a portion of thecore member604. The volume within thewell714 is sufficient to also accommodate at least a distal portion of thesecondary securement device694 which, as discussed above, can be an adhesive.
• A distal portion of thecore member604 comprises arecess718 configured to receive theannular protrusion710. In various embodiments the interface between theannular protrusion710 and therecess718 is configured to minimize or prevent any adhesive or other portion of thesecondary securement device694 from entering thelumen676. In other aspects, theflexible tip assembly600A is similar to the flexible toassembly600.
• FIG. 17 illustrates aflexible tip assembly600B as similar to theflexible tip assembly600 except as set forth below. Theflexible tip assembly600B is configured to minimize the likelihood of thehub608 becoming decoupled from thecore member604B, for example if forces in opposite directions are applied to the flexible member602 (e.g., distally directed) and the members648 (e.g., proximally directed) or a portion of theimpeller housing202. In one embodiment, this benefit is achieved by modifying thecore member604B to enable thecore member604B to directly connect to theproximal portion612 of theelongate body620. Thecore member604B can have an elongateddistal portion730 that extends distally of the distal end of thehub608. In one embodiment, elongateddistal portion730 comprises anenlarged portion734 in the distal end there of, a distal facingshoulder738, and thelumen676 extending therethrough. Theproximal portion612 of theelongate body620 can be received over theenlarged portion734 and advanced into engagement with the distal facingshoulder738. Securement of thecore member604B within thehub608 is similar to that described in connection with FIG.13A/B-16A.
• FIGS. 18A-18B illustrate an embodiment of aflexible tip assembly600C that is similar to the embodiment ofFIG. 17 except as set forth below. Ahub608C having an elongated distal portion is provided. The elongated distal portion can comprise adistal end742 that is disposed distally of theenlarged portion734 and thecore member604B when theflexible tip assembly600C is assembled. Thehub608C includes a taperedouter surface746 extending from thedistal end742 toward the proximal facingshoulder690. Thehub608C includes abore750 extending from the proximal end thereof to thedistal end742. Thebore750 is configured with different widths at different longitudinal positions. For example, thebore750 can be stepped such that it has a smallest diameter at or adjacent to the distal end. The diameter can be larger at the location where theenlarged portion734 of thecore member604B is disposed when thetip assembly600C is assembled. By decreasing the width of thebore750 at or distal to theenlarged portion734 thehub608C can impede axial, e.g., distal motion of thecore member604B relative to thehub608C. The diameter of thebore750 can be substantially constant along the length between the location where theenlarged portion734 is disposed and the location where a further enlargement of thebore750 is provided. The region of further enlargement can be configured to receive a portion of thecore member604B that couples with themembers648 of theimpeller housing202.
• FIG. 18A shows a transition from theflexible member602 to the taperedouter surface746 and from the tapered outer surface to theouter surface164 of the distal portion of thesheath assembly162. Such tapering can be advantageously configured to facilitate advancement of a percutaneous heart pump within the body. Theouter surface746 can act as a dilating structure in use. In certain embodiments, theflexible member602 is eliminated and the complexity of the distal section can be reduced by integrating a dilating structure into a distal portion of thehousing202 as discussed in connection withFIGS. 30-34 below.
• FIG. 19 shows another embodiment of a flexible tip assembly in which a plurality ofmembers648 of animpeller housing202 are joined at their distal ends by acircumferential structure760. In one variation, thecircumferential structure760 includes an arcuate structure extending at least between each of themembers648. The arcuate structure can be a ring that can be joined to each of themembers648 or a unitary ring-like arrangement bridging the distal ends of the members. In one embodiment, thecircumferential structure760 is disposed between thecore member604 and thehub608. In one embodiment, thecircumferential structure760 is received within a recess formed in the outer surface of thecore member604. Thecircumferential structure760 can enhance the security of the distal ends of themember648. In particular, by coupling the distal ends of themember648 together, twisting or movement due to torque on themembers648 or theimpeller housing202 can be reduced or eliminated.
• Another advantage of the embodiment ofFIG. 19 is that a rounded surface on the proximal portion of the core member is provided facing proximally toward theimpeller housing202. This rounded surface is one arrangement that can reduce the tendency of thrombogenesis at the proximal portion of the core member or adjacent to theimpeller housing202. Like other features discussed herein, this feature can be combined with those of other embodiments to provide additional embodiments.
• FIG. 19A illustrates another embodiment of aflexible tip assembly600D. Theflexible tip assembly600D can include ahub608D, a core member604D, and aflexible member602D. In some embodiments, thehub608D can have an increasing outer profile (e.g., outer diameter) along its length. In other embodiments, thehub608D can have a generally constant outer profile (e.g., outer diameter) along its length. Thehub608D can at least partially enclose the core member604D, described further below. Thehub608D can have one or more other characteristics of the hubs of the other flexible tip assemblies described herein. Thehub608D can be coupled with a proximal end of theflexible member602D. As illustrated inFIG. 19A, thehub608D can be coupled with theflexible member602D through the core member604D.
• The core member604D can include a rounded proximal surface facing proximally toward the impeller housing. As described herein, this rounded surface is one arrangement that can reduce the tendency of blood to pool in or adjacent to the impeller housing.
• The core member604D can have an elongateddistal portion730D that extends distally of the distal end of thehub608D. In one embodiment, elongateddistal portion730D comprises anenlarged portion734 in the distal end thereof, a distal facingshoulder738D, and alumen676D extending therethrough. The proximal portion612D of theelongate body620D can be received over theenlarged portion734D and advanced into engagement with the distal facingshoulder738D. Securement of thecore member604B within thehub608D can be similar to that described in connection with FIG.13A/B-16A.
• Theflexible member602D, which can be an elongate tubular member, can take any suitable form, but as illustrated inFIG. 19A, can include a proximal portion612D, adistal portion616D, and anintermediate portion620D extending therebetween. Thedistal portion616D can advantageously be made atraumatic, for example by including a tapered portion as illustrated inFIG. 19A, The proximal portion612D can be configured to be coupled with (e.g., advanced over a portion of) the core member604D, for example, via friction fit and/or an adhesive. In some embodiments, the proximal portion612D can have a tapered outer diameter that tapers distally towards theintermediate portion620D. The tapered outer diameter of the proximal portion612D can advantageously contribute to the atraumatic and pliable nature of theflexible member602D through a gradually decreasing wall thickness (stiffness) from proximal to distal portion of the member. As illustrated inFIG. 19A, theintermediate portion620D can be curved and/or can include a constant outer diameter. The curvature of theintermediate portion620D can take any suitable form, such as those described herein with respect to theatraumatic tip182. For example, theintermediate portion620D can take the shape of a j-tip or a pigtail tip. In yet another example, the distal-most end of theintermediate portion620D can curve around such that thedistal portion616D is generally perpendicular to the proximal-most end of theintermediate portion620D, as illustrated inFIG. 19A. As illustrated inFIG. 19A, thedistal portion616D can have a tapered outer diameter that can be configured to reduce trauma to the patient upon insertion and/or retrieval. Advantageously, although the outer diameters of the proximal portion612D and thedistal portion616D may taper distally, the inner diameter of these structures can remain constant, e.g., thelumen676D that extends through theflexible tip assembly600D can have a constant diameter.
• As illustrated inFIG. 19A, theflexible tip assembly600D can be configured to be coupled with thedistal members648D (e.g., structural members) of the impeller housing as described herein. For example, thedistal members648D can be received within a space created between the core member604D and thehub608D. Theflexible tip assembly600D can include a locking device as described herein that is disposed between thedistal members648D and thehub608D to prevent theflexible member602D from being separated from thedistal members648D. Advantageously, the components of the various flexible tip assemblies described herein can be interchangeable, as desired by those skilled in the art.
• 2. Unitary Hub Configurations Joining Flexible Tip to Impeller Housing
• While the foregoing embodiments provide advantages as discussed above, other embodiments are simplified in that they include a unitary hub structure and enable coupling of the hub to a distal portion of an impeller housing. In certain unitary hub embodiments, a distal portion of an impeller housing is insertable in a secure manner into slots in a hub. In other embodiments, the hub can be molded around a distal portion of an impeller housing with the distal portion having features to enhance the mechanical connection between these components.
• FIG. 20 illustrates further features for coupling portions of a flexible tip assembly similar to those discussed above in which a plurality ofslots784 is formed in a proximal aspect of an atraumatic tip. The atraumatic tip can include a flexible J-tip (e.g., an atraumatic tip) member and ahub788 formed with or coupled with the J-tip member, similar to those described above or formed as a unitary body. Theslots784 can be formed in a proximal end of the body of thehub788 and can be configured to receive and be secured to distal end portions of a plurality ofmembers792, which extend from or form a portion of theimpeller housing202. Themembers792 can be adapted to be inserted into theslots784. In one arrangement, the end portion of themembers792 can include a locking feature configured to be engaged by a receiving feature in a proximal aspect of thehub788. In one embodiment, the receiving feature can be a narrow aperture into a wider portion of theslot784. In one embodiment, the locking feature on themembers792 can include an enlarged section that is adapted to be insertable through the receiving feature but not to be retractable under forces experienced in the use in the body. The enlarged section can include as a barb or a plurality of barbs in some embodiments.
• Although the receiving feature and locking feature described in connection withFIG. 20 is sufficient to provide a robust connection between themembers792 and theslots784, a further enhancement of the flexible tip assembly can include an adhesive or other securement device at least partially disposed in theslots784. In some embodiments, where provided, the adhesive can be configured to substantially fill theslots784 to reduce any space for blood pooling around the tip assembly, which could lead to thrombus formation. In one variation, theslots784 are covered with a material that prevents pooling around the tip assembly without providing an adhesive or other device for providing securement.
• FIG. 21-21B illustrate other embodiments for enhancing the securing of a connection between a distal portion of an impeller housing and a hub.
• InFIG. 21, a distal portion of amember796 forming a distal portion of a variation of theimpeller housing202 includes a feature for integrating themember796 with a hub body or other component of a flexible tip assembly. In one embodiment, the feature for integrating themember796 comprises a through-hole800 through which a moldable material may flow or bridge. In other words, the through-hole800 permits a first portion of molded material to be formed on an inside portion of themember796, a second portion of molded material to be formed on an outside portion of themember796 and a third portion to extend through the through-hole800 to integrally form with the first and second portions to create a unitary body through and surrounding themember796. The arrangement ofFIG. 21 is advantageous for use in an insert-molding process. In one variation of the embodiment ofFIG. 21, the through-hole800 is replaced with a recess that extends only partly through the thickness of themember796. The recess is configured such that a volume of material that forms a hub into which themember796 can be incorporated can be received therein. A step or ledge is formed between the recess and the surface of themember796. Interactions between this step or ledge and material of the hub spanning across the step or ledge limits or prevents relative movement therebetween.
• FIG. 21A shows details of a distal portion of one embodiment of animpeller housing202A having amesh structure203A. Details of variations of the pattern of the mesh structure are set forth in U.S. application Ser. No. 12/829,359, filed Jul. 1, 2010 and in U.S. Pat. No. 7,841,976, issued Nov. 30, 2010. These documents are hereby incorporated by reference herein in their entirety for all purposes.FIG. 21A shows that adistal portion806 of themesh203A includes a plurality ofelongate filaments808 extending fromdistal apices809 of themesh203A. Theelongate filaments808 terminate in asecurement feature810. In the embodiment ofFIG. 21A, thesecurement feature810 is the distal most structure of themesh203A. Thesecurement feature810 comprises a circular structure branching laterally from a longitudinal axis of each of thefilaments808. The circular structure can be an annulus as illustrated inFIG. 21A or can be a disc that is configured to enhance securement of thefilament808 to a hub, similar to thehub788 or to other distal structure. For example, a disc could be provided with a recess or cavity on the inner side or outer side of themesh structure203A. In another variation a disc could be provided with one or more protrusions on one or more of the inside and outside of themesh203A.
• FIG. 21B is a variation of the structure ofFIG. 21A with modifiedfilaments808A that are configured to provide for securement of thedistal portion806 over adistal length812 rather than at the distal end of the filament as inFIG. 21A.FIG. 21B shows that in one embodiment, each of thefilaments808A can be provided with a plurality of securement features810A disposed along thedistal length812. In one embodiment, more than onesecurement feature810A is provided. As discussed above, the securement features810A can be through-holes recesses, or protrusions. As shown, three securement features configured as through-holes can be provided along thedistal length812 of each of thefilaments808A. By providing a plurality of securement features810A, the coupling can be spread over multiple points, providing redundancy in the securement to assure that the mesh will not be inadvertently detached from a hub with which it is connected. Also, by securing these components over a length, any twisting of thefilaments808A relative to a hub due to a torque applied to either structure will be reduced or eliminated.
B. Impeller Housing Configurations
• Theimpeller housing202 provides critical functions for theheart pump10.
• A key functional capability of thehousing202 in certain embodiments is to be able to significantly change in diameter, e.g., to be collapsed and expanded, repeatedly. Also, in certain embodiment thehousing202 is configured to deform in use in response to the approach of theimpeller blades212 as a way to manage separation between the blades and an inner wall of thehousing202.
• 1. Housing Configurations Using Shape Memory Materials
• FIGS. 2 and 4A illustrate expanded arrangements of thehousing202. In a collapsed state, thehousing202 and theimpeller blades212 are collapsed into a profile no larger than the inner diameter of thesheath assembly162. In the course of using thepump100, thehousing202 may be cycled between the collapsed and expanded configurations multiple times.
• The intended deformability of the housing is facilitated by one or both of structure and material choices. In some embodiments, at least a portion of thehousing202 can be formed from a shape memory material. Shape memory materials include materials that will expand to a predetermined state after being compressed or otherwise stressed. For example, a suitable material will permit thehousing202 to expand from a collapsed state within the transverse profile of the sheath to the expanded state ofFIGS. 4A-4B. Shape memory materials can also include materials capable of reversibly deforming and/or changing shape in response to a temperature change. Examples of suitable shape memory alloys include, but are not limited to, nickel-titanium (nitinol), copper-zinc, copper-zinc-aluminum, copper-aluminum-nickel, and gold-cadmium. In some embodiments, at least a portion of thehousing202 can be formed from nitinol. In one embodiment, essentially theentire housing202 can be formed from nitinol. In other embodiments, other shape memory materials, such as shape memory polymers and/or ceramics, can be used. In yet other embodiments, at least a portion of thehousing202 may not be formed from a shape memory material. For example, in some embodiments, at least a portion of thehousing202 can be formed from stainless steel. Thehousing202 can comprise commercially available materials that provide suitable collapsibility or expandability.
• Advantageously, shape memory materials can undergo significant deflections and deformation, yet maintain rigidity. Expansion can be due to the elasticity of the material or due to exposure to temperatures above a specific value. Accordingly, incorporating a shape memory material into thehousing202 can contribute to the ability of thehousing202 to significantly change in diameter (e.g., collapse and/or expand radially). Thus, in some embodiments, thehousing202 can be radially collapsible and configured for percutaneous insertion, while also being expandable to an operable diameter to allow theimpeller assembly116 to expand to an operable configuration.
• 2. Stiffened and Relaxed Impeller Housing Configurations
• Depending on the performance desired, variations of theimpeller housing202 can have enhanced stiffness or relaxed stiffness. As discussed above, one ormore blades212 of theimpeller200 are disposed and rotate within thehousing202. There is a nominal gap between theblades212 and thehousing200 in the rest state. The operation of thepump100 is highly dynamic, however, because many of the components of the pump are flexible and the pump is positioned in dynamic anatomical structures. Accordingly, the gap between theblades212 and the housing202 (also called tip-gap) can be dynamic in some embodiments. The tip gap can be controlled by enhancing the stiffness of one or more structures defining the gap, e.g., minimizing deflection of thehousing202 relative to the impeller blade(s)212 during operation. Also,FIGS. 26-29 illustrate embodiments for reducing flow disturbing effects at inlet and outlet locations, some of which involve enhancing stiffness of the housing. Enhancing flexibility is a strategy for enabling thehousing202 to react to pressure to move away from the blade(s)212, as illustrated by the embodiments ofFIGS. 22 and 23.
• Controlling tip-gap can be advantageously employed in some embodiments to compensate for movement of the catheter pump system. For instance, external forces can be applied to the impeller housing during manipulation or operation of the heart pump. These external forces may cause the impeller housing to deflect inwardly toward the blades and can cause contact between the housing and the blades. Maintaining sufficiently large tip-gap can therefore prevent undesirable contact between the impeller housing and the blades of the impeller. Example of embodiments that can help to maintain sufficient tip-gap by reinforcing or stiffening a proximal portion and/or an expandable portion of the impeller housing are discussed further in connection withFIGS. 24 and 25. Example of embodiments that help to isolate a zone of the impeller housing disposed about the blades from distal forces applied to the impeller housing distal of the blades are discussed in connection withFIG. 35 and following.
• In some embodiments, the pressure created by the operation of the impeller blades can cause the coating material covering the impeller housing to deflect. Large deflections of the coating material may be undesirable if the coating contacts the blades during operation, while in other embodiments, at least some deflection of the coating may be desirable (e.g., to prevent an overly rigid coating or to enable the coating to move away from a blade that is deflect toward the coating). The compliance of the coating can therefore be modulated by selecting a coating material with the desired material properties, by modulating the thickness of the coating, and determining the appropriate cell size in which the coating is formed, as discussed herein.
• a. Impeller Housing Having Stiffened Configurations for Reducing Housing Wall Deflection
• In one embodiment, thehousing202 is stiffened to limit movement of a wall of thehousing202. Factors such as pressures or pressure gradients along the length of or transversely across thehousing202 and loads applied to the impeller,impeller blades212, or tip of theimpeller assembly116 can cause the clearance between theblades212 and an inner surface of thehousing202 to vary. Other factors include varying pressure in a heart chamber or in a blood vessel adjacent the heart due to the heart being in systole and diastole, which can cause thehousing202 to dynamically change shape if the ventricular walls collapse during systole, which can affect the clearance between the blades and the inner wall of thehousing202. In addition, manipulation or operation of the device can induce external forces on the housing, which can also vary the clearance between theblades212 and the inner surface of the housing.
• There are different ways to modulate stiffness of the housing and each of these characteristic can be applied to any section of the housing. In other words, the housing is capable of having different stiffnesses at different regions attributed to a mix and match of different characteristics. In one embodiment, thehousing202 is configured to not flex in response to operational conditions so that a clearance distribution along the length of the cannula is kept above a minimum. For example, the stiffness of thehousing202 can be increased to limit movement of the housing relative to the impeller blades in response to external pressures or factors. To increase the stiffness in any portion of the housing, the density of the mesh can be increased. For example, more rings per unit length can be provided to make thehousing202 less responsive to operational conditions. In another embodiment, the geometry of the circumferential rings can be changed, such as by thickening the cross-section of the individual rings to be stiffer, thus making thehousing202 stiffer. In another embodiment, a thicker or less compliant coating can be provided over a portion of the length of the housing to enhance the stiffness in the coated region. Another embodiment would provide an enhanced connectedness between adjacent rings, such as by increasing the number of connectors between adjacent rings to increase the stiffness of thehousing202. In another embodiment, stiffer axial connectors can be provided between adjacent rings to reduce changes in clearance at the stiffened region.
• FIGS. 26-29 illustrate further embodiments that advantageously control the stiffness of thehousing202 to enhance performance. The hydrodynamic performance of theheart pump10 may be impaired by the flexibility of thehousing202 at an inlet110 into thehousing202. As discussed above, thehousing202 can include a mesh-like structure203 that is covered or coated with acoating204 to provide a cannula structure. The cannula structure provides a blood flow channel through thehousing202. In some operational conditions, flapping or other deformation of thecoating204 at inlet110 may result in an undesirable or too large pressure drop for a given blood flow rate, and may also result in blood damage via hemolysis and/or thrombus formation. Accordingly, it is desirable to providehousing202 with a stiffened region at the inlet110 while maintaining the overall flexibility of the cannula both to accommodate the patient's vascular geometry and to facilitate the compressibility of the cannula for percutaneous insertion.
• The expandable portion of thehousing202 may be provided with various inlet and outlet features.
• FIG. 26 shows the distal end of anexpandable housing202 formed using any suitable manufacturing technique to provide athicker coating204 and alip976, e.g., a distally oriented protrusion, at the free end of thehousing202. InFIG. 26, the thickness of thelip976 has been greatly exaggerated to make thelip976 more visible. Although thicker, in some embodiments, the enhanced thickness is not so great as to substantially increase the crossing profile of thecatheter assembly100. The increased thickness ofcoating204 and thelip976 improve the structural stiffness of the cannula inlet.
• The benefits of cannula shaping may also be applied to anoutlet111 at the proximal end of thehousing202.FIGS. 27 and 28 show a proximal end portion of acannula202 that can be shaped using any suitable process. Theoutlet111 has adiffuser arrangement980 at the proximal end of thehousing202. Thehousing202 ofFIGS. 27 and 28 may have an outwardly flaredportion982 of theoutlet111 and optionally acrisp lip984, e.g., a ring, at the proximal end of thecoating204. In addition tolip984, theoutlet111 may include a plurality ofleaflets986 defined by the end wire structure ofmesh203 and filled with the material ofcoating204. In some embodiments, each cell or portion of the mesh can be completely filled with the coating material such that no cell is only partially filled with the coating material. Thus, in some embodiments, the coating material can be completely surrounded by struts in the housing.
• The complex geometry of thehousing202 around theoutlet111 can be configured to cooperate with the impeller assembly disposed in thehousing202. For example, as shown inFIG. 29, in some embodiments adiffuser990 can be disposed downstream of theblades212 of the impeller. Thediffuser990 can have a tapered outer surface that is configured to create a divergent flow in thehousing202. The outwardly flaredportion982 can advantageously accommodate the flow regime induced by theimpeller blades212 and thediffuser990. For example, generally axial flow (from left to right in the figure) can be altered to have a radial component by thediffuser990. Because thehousing202 has the outwardly flaredportion982 at the location of thediffuser990, the radial flow is accommodated without creating excessive back-pressure in thehousing202. The dashed line inFIG. 29 shows that in one embodiment, the outwardly flaredportion982 has a largest radially extent at substantially the same axial position in the heart pump illustrated therein as the largest radial extent of thediffuser990. Thus the outwardly flaredportion982 enables higher flows for comparable pump configurations compared to an impeller assembly having a diffuser and being mounted in a straight housing. The outwardly flaredportion982 also could minimize hemolysis by reducing radial concentration of red blood cells at the axial position of thediffuser990.
• Theleaflets986 are advantageous in that they spread out axially the position of the pressure drop that occurs at theoutlet111 from the inside of thehousing202 to the outside thereof. If the pressure drop across the inside-to-outside boundary were concentrated at a single axial location, a generally conical flow pattern might result. Although such a pattern may be acceptable, it would be unlike typical arterial flow which is more random due to the varying pressure in the arterial system. In contrast, by providing theleaflets986 the outflow is much more random and more consistent with native vascular, e.g., arterial flow.
• b. Impeller Housing Having Enhanced Flexibility for Dynamic Tip-Gap Control
• In another embodiment, the stiffness of thehousing202 can be reduced to permit the housing to flex in response to conditions such as instantaneous pressure rise at the wall. Such a pressure rise may result from theblades212 being deflected toward the inner wall of thehousing202. By reducing the stiffness of thehousing202, the wall is able to expand or be deflected in an advantageous manner. A reduction of the stiffness of thehousing202 can be achieved by reducing the density of the mesh in the region where stiffness is desired to be reduced. In another embodiment, the stiffness of thehousing202 can be reduced by providing fewer circumferential rings or other members per unit length in the region to be made less stiff. In one embodiment illustrated byFIGS. 22 and 23, thehousing202 can be made less stiff by reducing the stiffness of individual components of the mesh, such as making the rings thinner in a region where enhanced flexibility is desired. For example,FIG. 22B shows a detail view of a tip ofblade212 of an impeller adjacent an inner wall W of thehousing202. A gap G between the wall W and theblade212 corresponds to the clearance between theblade212 and the wall W.
• InFIG. 22B, the gap G is illustrated as being very small. A too-small gap can result in hemolysis as discussed herein.FIG. 23 illustrates how a pressureadaptive housing202A can be configured to maintain an acceptable gap. In particular, thehousing202A is made more flexible at least in the region of theblades212. As a result, the wall W of thehousing202A will be deflected by local pressures due to the operation of the impeller of which theblades212 are a part. More particularly, thehousing202A can be configured with a flexible impeller zone207 (e.g., void or cell area defined by struts with coating material) that will be radially deformed in certain operational conditions. For example, if the impeller is deflected from a nominal central position toward the wall of thehousing202A, an area of thehousing202A at the same axial position, e.g.,flexible impeller zone207, will be radially deflected outward. This is shown inFIG. 23B in which a portion of thehousing202A corresponding generally to theflexible impeller zone207, e.g., when in use, protrudes from an otherwise continuous cylindrical surface of the wall W to form an internal channel within thehousing202A corresponding to the shape of theblade212. The protruding portion creates a gap G1 that is greater than the gap G inFIG. 22B. The enlarged gap G1 corresponds to more clearance between theblade212 and the wall W so that red blood cells or other blood components will not be damaged flowing through the impeller zone. Those skilled in the art may appreciate that the protruding portion of thehousing202A may not always protrude from the otherwise continuous cylindrical surface of the wall W. For example, the protruding portion may be configured to protrude only when the heart pump is in use, e.g., when the impeller is deflected under operating conditions.
• A variety of techniques can be used to cause thehousing202A to provide an enlarged gap or to protrude radially at the impeller zone. In one embodiment, thehousing202 is coated along its length, but the coating is made thinner in a region where enhanced flexibility would be advantageous. In another arrangement, it may be advantageous to increase the flexibility of the housing by reducing the number of axial connectors or entirely eliminating connectors between adjacent rings in the region to be made more flexible.
• Additional advantages of enabling thehousing202 to be adaptive to the pressures to which it is exposed in use may result. For example, in some embodiments, pressure responsive shaping of thehousing202 immediately adjacent to in the impeller inlet plane to be straight or slightly converging or slightly diverging may be useful to optimize radial velocity profile to the impeller. These arrangements may be the result of exposing ahousing202 that is configured to be responsive to differences in pressure across cannula due to blood pressure and instantaneous pump through-flow velocity and other factors discussed above. This arrangement may be preferable to requiring significant bell-mouth inlet convergence shaping well upstream of impeller.
• Adaptive cannula shaping can provide a more robust configuration. For example, clearances between the impeller blade tips and the cannula inner surface are very difficult to control with realistic manufacturing tolerances and due to deflections in the impeller shaft that can occur due to the impeller shaft not being a perfectly rigid element. If this clearance is too wide, there is a loss of performance. If it is too small, undesirably high fluidic stresses can occur and result in unacceptably high hemolysis, or even result in potentially damaging contact between the impeller blade tip and the cannula inner surface.
• Although shaping of the cannula structure for significant bell-mouth inlet convergence generally can be helpful, other important factors include impeller radial runout and shaft deflection. By having a cannula coating that deflects in response to the localized pressure force produced at and near the impeller blade tip, a desirable tip-to-cannula gap can be maintained.
• In some embodiment, a portion of thehousing202 downstream of theimpeller blades212 is made pressure responsive such that the shape of the housing is induced by the ambient pressure. For example, thehousing202 can be configured to present a shape that would provide flow benefits downstream of theblades212. Thehousing202 can be configured to be diverging downstream of the impeller exit plane in a manner that optimizes diffusion downstream of the impeller. Thehousing202 can be configured downstream of the impeller exit plane in a manner that optimizes deswirl in the downstream flow region. Such a shaping can be induced by pressure in thehousing202 during operation or by other conditions, such as blood pressure and instantaneous pump throughflow velocity.
• As discussed above, advantages can be achieved by making thehousing202 pressure adaptive or by configuring thecannula202 to respond in a predicted manner to the ambient conditions. This can result in a gentler handling of red blood cells and other blood components that can be damaged by conditions such as a too narrow gap between theblades212 and thehousing202.
C. Impeller Housing Support Enhancement
• Various techniques are discussed above for enhancing the stiffness of thehousing202. Another technique for controlling clearance within the flow channel of thehousing202 is to increase the stiffness of the area within and adjacent to where the impeller is mounted.FIGS. 24-25 illustrate techniques for increasing the stiffness between the expandable portion of thehousing202 and the non-expandable section of the catheter assembly112 proximally thereof. By stiffening a proximal portion of theimpeller housing202, transverse deviations of the proximal portion of thehousing202 or components housed therein can be reduced. A stiffening structure can be provided to maintain theimpeller shaft204 in a centered position within theimpeller housing202. These arrangements are particularly useful where theimpeller shaft204 is cantilevered from the proximal portion of theimpeller housing202. These features can be combined with an assembly that provides distal support to theimpeller shaft204, as described in U.S. application Ser. No. 12/829,359.
• FIG. 24 illustrates animpeller housing900 that is similar to theimpeller housing202 except as described differently below. Theimpeller housing900 includes an expandabledistal portion904 and aproximal portion908 that has a generally fixed profile. In one embodiment theproximal portion908 houses a proximal portion of impeller similar to theimpeller200. An impeller can be supported in a cantilevered manner from theproximal portion908 of the housing902.
• A plurality of members912 extends between theproximal portion908 and the expandabledistal portion904. The plurality of members912 can include a first group ofstruts912A to provide a secure connection between the distal andproximal portions904,908. A plurality ofgaps916 defined betweenadjacent struts912A can be configured to permit blood flowing from an upstream location through thehousing900 to exit the housing at a downstream location. For example thegaps916 can be disposed within a portion of the vasculature, e.g., the pulmonary artery or the aorta while an intake in of the pump of which thehousing900 is a part can be disposed in a fluid source, such as a chamber of the heart. When the pump including theimpeller housing900 is in operation, blood drawn from the left ventricle can flow through thehousing900 and be expelled through thegaps916 into the aorta.
• In one embodiment the proximal end of theproximal portion908 of theimpeller housing900 is coupled to acatheter body920 similar to thecatheter body120 discussed above.
• In certain embodiments it is desired to stiffen a proximal section of theimpeller housing900. This can be achieved by providing one or more stiffening members coupled with theproximal portion908 and adistal portion904. For example, in the embodiment ofFIG. 24 a second group ofstruts912B is provided between distal andproximal portions904,908. Thestruts912B are located on opposite sides of theimpeller housing900. Each of thestruts912B includes adistal end918 coupled with thedistal portion904 and aproximal end922 coupled with theproximal portion908. In one embodiment, thedistal end918 is coupled with thedistal portion904 at approximately the same longitudinal position as the longitudinal position where thestruts912A connect to thedistal portion904.
• In one embodiment, theproximal end922 of thestruts912B are coupled with theproximal portion908 at a longitudinal position that is proximal of the longitudinal position where thestruts912A are coupled with theproximal portion908. In one embodiment, each of thestruts912B is coupled with theproximal portion908 at the same longitudinal position. In one arrangement, acircumferential member924, which can be a ring, extends between and couples the proximal ends922 of thestruts912B.
• FIG. 24 illustrates embodiments that advantageously stiffen theimpeller housing900, particularly in the region of theproximal portion908 and in at least a portion of thedistal portion904 in which impeller operates. In part, the enhanced stiffness is due to a triangular structure formed betweenadjacent struts912A,912B and a length of theproximal portion908 extending between the proximal ends of thestruts912A,912B. This triangular structure provides a rigid configuration like a truss that resists deflection of this proximal zone from a central longitudinal axis of theimpeller housing900.
• Depending on the materials and arrangement ofimpeller housing900, the forced to collapse the expandabledistal portion904 can be increased by the presence of thestruts912B.
• FIG. 25 illustrates another embodiment of animpeller housing930 in which the stiffening benefit ofstruts912B is provided while maintaining or reducing the collapsing force needed to collapse the expandabledistal portion904. Theimpeller housing930 is similar to theimpeller housing900 except as described differently below. In theimpeller housing930, at least thestruts912B are coupled with the structure that is locked in an axial position in a first configuration and that is capable of sliding proximally to a second axial position in a second configuration.
• In one embodiment the proximal ends922 of thestruts912B are coupled with a slidablecircumferential structure924B. The slidablecircumferential structure924B can comprise a short sleeve disposed aboutproximal portion908. In one embodiment alocking device934 is provided to hold thecircumferential structure924B in a first axial position about theproximal portion908. Thelocking device934 may have a first configuration in which at least one of a shoulder is provided to limit the axial travel of thecircumferential structure924B. In one embodiment, a distal-facing shoulder is provided. In another embodiment, proximal and distal-facing shoulders capture the circumferential structure therebetween. In one embodiment, thelocking device934 includes a rampedproximal portion938. Thelocking device934 can be actuated to a second configuration in which thecircumferential structure924B is permitted to slide proximally on theproximal portion908. In one embodiment, advancement of thedistal end170 of thesheath assembly162 into engagement with the rampedproximal portion938 causes the forward facing shoulder of thelocking device934 to be retracted such that the forward facing shoulder does not prevent proximal movement of thecircumferential structure924B. Further advance of thedistal end170 of thesheath assembly162 causes the distal end to engage thestruts912B. Continued advancement of thedistal end170 of thesheath162 causes the struts912bto be collapsed against theproximal portion908 and also causes thecircumferential structure924B to slide along theproximal portion908. Depending on the configuration of theimpeller housing930, thecircumferential structure924B can slide proximally or distally during the collapsing of thedistal portion904.
• In another embodiment, thelocking device934 can be actuated by a mechanism disposed on the proximal end of modified version of thepump100. For example, a tension member such as a wire can be disposed within the catheter assembly112. For example, a pull wire can be disposed within a peripheral lumen formed in a catheter body similar to thecatheter body120. For example, one of thelumens282 illustrated inFIG. 7-7C can be configured to house a pull wire. Actuation of the pull wire from the proximal end of the modified pump can cause thelocking device934 to disengage from thecircumferential structure924B, e.g., to be actuated to a retracted position, permitting movement of thecircumferential structure924B.
• Thelocking device934 can be configured with a proximal locking component and a distal locking component in one embodiment. Where proximal and distal locking components are provided, axial sliding of thecircumferential structure924B is prevented in both the proximal and distal directions when thelocking device934 is actuated to a locked configuration.
• In one embodiment, thelocking device934 includes a retractable latch.
• The enhancement of the stiffness of the proximal portion and a proximal zone of the distal, expandable portion of an impeller housing in embodiments illustrated byFIGS. 24-25 is advantageous in that it provides one approach to controlling undesirable interactions betweenimpeller blades212 and inner surfaces of the impeller housing. Contact betweenimpeller blades212 and inner surface of the impeller housing can lead to damage to certain blood components such as red blood cells. At the relatively high blood pump pressures and flows anticipated in thepump100, minimizing hemolysis is a significant advantage.
• III. Catheter Assembly Having Integral Dilating Structure
• FIGS. 30-33 illustrate acatheter assembly1000 with asheath assembly1028 and atip assembly1004 having anintegral dilating structure1008. Thecatheter assembly1000 can be used with a heart pump, as discussed above, and can provide several advantages. For example, by integrating the dilatingstructure1008 into the tip assembly, the tip assembly can be used to dilate anatomical structures such as the aortic valve. Also, the configuration of the dilatingstructure1008 can be selected to space an intake structure from the anatomy to prevent the anatomy from being sucked into the intake. These embodiments advantageously can be made with fewer parts and benefit from not including a distal flexible member as in some of the other embodiments herein.
• FIG. 31 shows that thecatheter assembly1000 is capable of percutaneous insertion and includes animpeller1012 having one or morefoldable blades1016 and anexpandable housing1020 surrounding the impeller. Thehousing1020 can be configured as a cannula in some embodiments. Thehousing1020 has a collapsed configuration for delivery to a desired location within the body and an expanded configuration in which the impeller can rotate to pump blood. The collapsed configuration is illustrated inFIG. 30 and the expanded configuration is illustrated inFIGS. 31-33.FIG. 34 shows thecatheter assembly1000 deployed in the anatomy and in the expanded condition.
• Thecatheter assembly1000 includes thesheath assembly1028 that is similar to those hereinbefore described and can be advanced over aguidewire1024. Theguidewire1024 can be used to access the anatomy, e.g., the left ventricle as illustrated inFIG. 34.
• Thecatheter assembly1000 can track over theguidewire1024 to a selected position, e.g., with a proximal portion of theimpeller housing1020 residing in the ascending aorta, the distal portion of the impeller housing1020 (including the dilating structure1008) residing within the left ventricle, and theimpeller housing1020 generally crossing the aortic valve. Optionally, the dilatingstructure1008, positioned within the left ventricle, can then be urged into contact with the aortic valve, e.g., at the ventricular side of the aortic valve, to separate the aortic valve leaflets from each other. This can advantageously enable thecatheter assembly1000 to be advanced through the aortic valve into the heart in a minimally traumatic manner, protecting the aortic valve. In other embodiments, for example as illustrated inFIG. 34, the dilatingstructure1008 may be positioned sufficiently distal to the aortic valve such that it does not contact the aortic valve upon expansion/dilation. Thereafter, thedistal portion1032 of thehousing1020 is disposed in the left ventricle and a proximal portion of thehousing1020 is located in the ascending aorta, as illustrated inFIG. 34.
• When positioned in the anatomy, thecatheter assembly1000 extends proximally to a peripheral access site, such as a femoral access site. After delivery, theguidewire1024 can be retracted by applying a proximally directed force while holding the proximal end of the catheter assembly in place.
• FIG. 34 illustrates a method in which theguidewire1024 is left in place after thesheath1028, shown inFIG. 32 has been retracted. In this method, thehousing1020 is expanded before theguidewire1024 is removed. In another method theguidewire1024 is first removed, then thesheath assembly1028 is retracted permitting thehousing1020 and theimpeller blades1016 to be expanded. Those skilled in the art may appreciate that regardless of the order in which theguidewire1024 and thesheath1028 are retracted, theguidewire1024 should be completely retracted prior to and/or during operation of the device (e.g., theguidewire1024 should be removed before the device is operated.)
• FIGS. 31 and 33 show that thedilator1008 includes aport1040 configured to receive theguidewire1024. Theguidewire1024 can also be advanced through theimpeller1012 in various embodiments. Further features that facilitate advancement of a guidewire through an impeller are described in U.S. patent application Ser. No. 12/829,359, filed Jul. 1, 2010. Thedilator1008 can be configured as a plurality ofarms1044 extending outward and proximally from theport1040. Thearms1044 form a substantially continuous surface extending proximally from theport1040 in the collapsed state (seeFIG. 30) and a substantially blunt structure in the expanded state (seeFIG. 32-33). More particularly eacharm1044 can extend from acentral hub1048 disposed around theport1040 to aproximal end1052 disposed away from thehub1048. Theproximal end1052 may be joined to adistal end1054 of an elongatestructural member1058, aproximal end1062 of the member extending from a mesh of expandable members forming thehousing1020.
• As in other embodiments, thehousing1020 can optionally include a covering or coating and in the embodiment ofFIGS. 30-34, adistal portion1070 of the coating extends a portion of the length of theelongate members1058.FIG. 32 illustrates that coating the distal end presents a transverse size (e.g., cross-sectional area, diameter, or height in the view ofFIG. 32) that is significant larger than the transverse size of the central portion of thehousing1020. This enables a gentle intake of blood into the lumen in thehousing1020. In other words, there is a much more gradual pressure change in the blood that flows from outside thestructural members1058, through themembers1058 and proximally across thedistal portion1070 into the lumen in thehousing1020. This provides a more atraumatic conveyance of blood into thecatheter assembly1000.
• Eacharm1044 may be configured to couple with a distal portion of thesheath assembly1028. In one embodiment, a proximal portion of eacharm1044 has a reduced thickness such that the distal end of thesheath assembly1028 can be urged up into abutment with aproximal ridge1072 of the thicker, distal portion of thearms1044. This sliding and abutting provides a minimum step up in diameter from the diameter of thearms1044 to the diameter of thesheath assembly1028 so that transition from thearms1044 to the sheath assembly will slide through the anatomy with ease.
• FIG. 33 illustrates arelief area1066 provided betweenadjacent arms1044 to enable thearms1044 to more closely conform to a gradually proximally expanding structure that would be suitable for dilating tissue.
• One advantage of the embodiments illustrated byFIGS. 30-34 is that thedilator1008, as an integrated part of the expandable housing structure, enables thecatheter assembly1000 to be advanced through the vasculature without an independent delivery sheath being disposed between thesheath assembly1028 and the patient, which is typical in percutaneous procedures. The elimination of the independent delivery sheath preserves a greater percentage of the crossing profile for thecatheter assembly1000. This can be advantageous in permitting an increase in the size of theimpeller1012, which can enhance flow output of a heart pump incorporating thecatheter assembly1000.
• Another advantage provided by thecatheter assembly1000 is that in the expanded state,wide openings1074 are provided between pairs of adjacent elongate atraumaticstructural members1058. Theopenings1074 provide efficient intake of blood in use. Additionally, the blunt configuration of this inlet portion overall greatly reduces the likelihood that the anatomy adjacent the intake will be sucked into the intake to interfere with operation of the pump. In other words, expansion of the cannula simultaneously expands the tip of thedilator1008, which serves to space the inlet of thecannula assembly1000 from the inner heart wall W and other structures within the heart during a pumping operation.
• IV. Impeller Assembly Having Load Isolation Configuration
• FIGS. 35-38 illustrate embodiments that advantageously isolate the portion of a housing (e.g., thehousing202,1020 or other housings described herein) in which an impeller operates from deflections that could be induced by the moving anatomy in which theheart pump10 operates. For example, in some embodiments, a housing (e.g., any housing described herein) can have a wall structure that is configured to minimize and/or reduce deflection in a proximal region of the housing. As discussed herein and in U.S. Provisional Application No. 61/430,129, filed Jan. 5, 2011, theheart pump10 operates more effectively when a controlled gap is provided between the spinningimpeller200 and the inner wall of thehousing202, which forms a cannula. This also applies to thehousing1020 andimpeller1012 of thecatheter assembly1000.
• FIG. 34 shows that thetip assembly1004 of thecatheter assembly1000 is disposed in the left ventricle and may be exposed in use to the movement of the beating heart, such as the wall W. This motion may adversely affect the alignment between theimpeller1012 and the inner wall of thehousing1020.
• FIG. 35 shows that movement at the distal portion of the housing202 (or housing1020) due to interaction with the wall W could result in bending at the proximal portion of the housing in the area where the impeller200 (or impeller1012) operates. A bending load L applied at thedistal end108 of thehousing202 or a transverse displacement D of thedistal end108 from a straight projection of the orientation of theproximal end104 can create atransition zone1090 adjacent to animpeller zone1092 where theimpeller200 operates. Having uniform stiffness along the length of thehousing202 distal theimpeller200 can potentially result in a substantially straight length of thehousing202 between thetransition1090 and thedistal end108. This can cause thetransition zone1090 to be localized adjacent to theimpeller200, which is disadvantageous when the cannula collapses where stress concentrates at the localized region. This can adversely affect the gap between the impeller and thehousing202.
• FIG. 36-36D illustrate in a flat form awall pattern1100 that can be used to form a structure similar to the cage ormesh structure203. Thepattern1100 includes a proximal portion1102 adistal portion1104 and anelongate pattern1106 extending therebetween.
• Theproximal portion1102 can take any form, but may be rigid enough to be securely coupled with the bearinghousing220. Theproximal portion1102 can form a generally fixed perimeter hollow cylinder configured to be fitted over the bearinghousing220. Thedistal portion1104 can be configured to have a low profile for delivery and to expand to permit efficient intake of blood, such as by forming openings similar to theopenings1074 discussed above when expanded. The low profile can be the same as or similar to or smaller than that of theproximal portion1102. In one embodiment, thedistal portion1104 is coupled with an atraumatic tip, such as illustrated and described in connection withFIGS. 13-21B. In another embodiment, thedistal portion1104 forms a portion of a dilating structure such as theintegrated dilating structure1008.
• Theelongated pattern1106 can take any suitable form, but may include a plurality of expandable zones with different rigidities to enable isolation of theimpeller zone1092 from the load L illustrated inFIG. 35. In one embodiment, theelongate pattern1106 includes a firstexpandable zone1108 disposed adjacent to theproximal zone1102. The firstexpandable zone1108 is configured to closely control the gap between an impeller and the inner wall of a housing into which thewall pattern1100 is incorporated. The firstexpandable zone1108 can be configured with the greatest rigidity of all the expandable zones in theelongated pattern1106. The firstexpandable zone1108 corresponds to the location of (e.g., is disposed over) an impeller such as theimpeller202 and can extend along approximately the proximal one third of theelongated pattern1106. In some embodiments, the expandable zone(s) distal of the firstexpandable zone1108 provide sufficient ability to isolate the impeller from the load L or displacement D (seeFIG. 35) that the length of the stiffest portion of the housing can be shortened to less than one-third the length of the housing.
• In one embodiment, theelongated pattern1106 comprises a plurality of zones of different rigidities distal of the firstexpandable zone1108. For example, at least one zone can be the same, more, or less rigid compared to the firstexpandable zone1108 depending on the flex pattern desired along the housing. In one embodiment, a secondexpandable zone1110 and the thirdexpandable zone1112 are both less rigid and disposed distally of the firstextendable zone1108. The secondexpandable zone1110 can be disposed between the firstexpandable zone1108 and the thirdexpandable zone1112. Thesecond zone1110 may have a rigidity that is less than that of the firstexpandable zone1108. In one embodiment, the thirdexpandable zone1112 has a rigidity that is less than the secondexpandable zone1110. In some embodiments, thesecond zone1110 has a greater ability to deflect in response to the load L or displacement D than does the firstexpandable zone1108. In some embodiments, thethird zone1112 has the greatest ability to deflect in response to the load L or displacement D of the first, second, andthird zones1108,1110,1112. It may even be desirable to configure the second and thirdexpandable zones1110,1112 to deform with the deformation. Thepattern1100 can be configured to deform most in the thirdexpandable zone1112 and progressively less proximally thereof toward the firstexpandable zone1108.
• Thedistal portion1104 can be considered a fourth expandable zone dispose distally of the thirdexpandable zone1112. In one embodiment thedistal portion1104 has a rigidity that is greater than that of the thirdexpandable zone1112. For example, at least aproximal section1104A of thedistal portion1104 can be configured to provide a rigidity that is similar to that of theproximal portion1102. In some embodiments, thedistal section1104B of thedistal portion1104 can be provided with a plurality of elongate gaps therebetween to provide generally unimpeded intake of blood as discussed above. Thedistal section1104B of thedistal portion1104 can also have enhanced flexibility to provide atraumatic interactions with the anatomy.
• FIG. 36A illustrates more detail of one embodiment of the firstexpandable zone1108. The firstexpandable zone1108 comprises aproximal end1116 comprising a plurality of longitudinally orientedmembers1118 coupled with theproximal portion1102. The firstexpandable zone1108 also includes a plurality of circumferentially orientedrings1120 arranged along the longitudinal axis of the pattern. Therings1120 may have a sinusoidal configuration. The number ofrings1120 can be varied, and may depend on the configuration of the impeller to be disposed within the housing into which thepattern1100 is incorporated. In one embodiment the firstexpandable zone1108 includes eightcircumferential rings1120, while in other embodiments the firstexpandable zone1108 includes six or sevencircumferential rings1120. A skilled artisan would understand that the firstexpandable zone1108 can include any suitable number ofrings1120.
• The circumferential rings1120 of the firstexpandable zone1108 may comprise a plurality of crests andtroughs1122,1124 that are distally and proximally oriented.FIG. 36A illustrates that thecrests1122 of a first ring in the firstexpandable zone1108 are overlap with (e.g., are nested within) thetroughs1124 of a secondcircumferential ring1120, where the second circumferential ring is located distal of the first circumferential ring. This arrangement enables aconnector1126 to extend substantially circumferentially from a first location on the first ring to a second location on the second ring. The first and second locations can be located just off (e.g., proximal of) acorresponding crest1122 and just off (e.g., distal of) acorresponding trough1124. Theconnector1126 is relatively short in one embodiment, e.g., having a length that is about equal to the width of the portion of therings1120 that extends between the crests andtroughs1122,1124.FIG. 38 illustrates an embodiment in which at least some circumferential connectors are widened to enhance stiffness of the structure. The width of the connectors1026 are about equal to or in some cases greater than the length thereof. In one embodiment, aconnector1126 provides a circumferential connection between a strut forming a crest and a strut forming a trough of differentadjacent rings1120. Accordingly, theconnector1126 can be referred to herein as a radial/adjacent connector. In the firstexpandable zone1108, theconnectors1126 are located at the same axial position such that a cross-section perpendicular to the length of thepattern1100 would intersect all of theconnectors1126.
• The nested arrangement of the crests andtroughs1122,1124 of the adjacent circumferential rings1120 (i.e., the proximity between adjacent crests and troughs) provides enhanced rigidity in the firstexpandable zone1108. In one embodiment, the nested arrangement of the crests andtroughs1122,1124 of the adjacent circumferential rings1120 is approximately 50% overlapped in width. In some arrangements, nesting of crests andtroughs1122,1124 is not provided, which would result in a more flexible structure all else remaining equal. In some arrangements, nesting of the crests andtroughs1122,1124 can be as much as 80% overlapped in width, or limited by the material and manufacturing capabilities, which would result in a less flexible structure all else remaining equal. By providingconnectors1126 between each adjacent crest andtroughs1122,1124 further enhancement of the rigidity of the firstexpandable zone1108 is provided.
• In one embodiment, aconnector1128 that is generally axially oriented is provided between adjacent circumferential rings1120. Theconnector1128 extends from afirst end1128A (e.g., a crest) coupled with proximal side of eachtrough1124 and asecond end1128B coupled with a side portion (e.g. an arm extending between a crest and trough) of acircumferential ring1120 disposed proximally of thefirst end1128A. Accordingly, theconnector1128 can be referred to herein as an axial-to-side connector. Theconnector1128 can take any suitable form, and in some embodiments are included mainly to facilitate collapsing of the housing into which thepattern1100 is incorporated. Theconnector1128 can be sinusoidal in form, for example having, in one example, a plurality of apices, such as at least three apices between the first and second ends1128A,1128B. In other embodiments, theconnectors1128 can be straight to provide greater rigidity to facilitate retraction of the housing into a sheath, as discussed above. In one arrangements, at least the proximal pair ofrings1120 are connected by variations of theconnectors1128 that are stiffened (e.g., made straight, thicker or wider) to reduce bending adjacent theproximal portion1102.
• The secondexpandable zone1110 can be made more flexible by any suitable means. For example,FIG. 36B illustrates that the secondextendable zone1110 can be configured with enhanced flexibility by eliminating theconnector1126 between at least some of therings1120.FIG. 36B illustrates that in one embodiment at least a plurality of (e.g., at least four)adjacent rings1120 are not connected to each other circumferentially, however in some embodiments at least five or sixadjacent rings1120 are not connected to each other circumferentially. Also, the secondexpandable zone1110 can be made more flexible by including aconnector1128′, which extends generally axially, instead ofconnector1128. In one embodiment, theconnector1128′ can be elongated, as compared toconnector1128, to provide enhanced flexibility. One technique for making theconnector1128′ longer thanconnector1128 is to connect thesecond end1128B′ with thetrough1124 of the next-proximal circumferential ring1120 instead of at a location on the next proximal ring between adjacent troughs and crests. By disposing the first and second ends1128A,1128B′ farther apart, theconnector1128′ can be made longer than an otherwisesimilar connector1128 to permit more apices along its length.
• Another technique for enhancing the flexibility of the secondexpandable zone1110 is to lengthen theconnector1128 and/or theconnector1128′ by increasing the amplitude of the waves along the length of the connector compared to the amplitude in the firstexpandable section1108. By increasing the amplitude, the connectors are made longer and are able to stretch and move upon application of a similar or lower force, thus being more flexible. Additionally, rather than having nesting between peaks and troughs of adjacent rings, further flexibility can be obtained by creating a gap between adjacent rings and progressively increasing the amount of gap.
• In one embodiment, the flexibility of theexpandable zone1110 is progressively greater in the distal direction. This can be accomplished by lengthening theconnectors1128 and/or theconnectors1128′ from one circumferential ring to the next along the length of the secondexpandable zone1110. For example, a proximal aspect of the secondexpandable zone1110 can includeconnectors1128′ with a first number of apices (e.g., five apices) and a distal aspect of the secondextendable zone1110 can includeconnectors1128′ with a second number of apices greater than the first number (e.g., seven apices). Or, a proximal aspect of the secondexpandable zone1110 can includeconnectors1128′ with apices having a first average amplitude and a distal aspect of the secondextendable zone1110 can includeconnectors1128′ with apices having a second average amplitude greater than the first average amplitude.
• Another technique for enhancing the flexibility of an expandable zone is to progressively decrease the amount of nesting of peaks and troughs of adjacent rings. For example, the crests and troughs of a first adjacent pair ofcircumferential rings1120 can overlap to a greater extent than those of a second adjacent pair ofcircumferential rings1120 where the first pair is proximal of the second pair.
• As show inFIG. 36C, a thirdexpandable zone1112 can be configured for greater flexibility than the secondexpandable zone1110 by decreasing the amount of overlap between adjacent crests and troughs of adjacent circumferential rings1120. For example, a first pair ofadjacent rings1120A and a second pair ofadjacent rings1120B are provided with overlap of length OL1 and OL2 respectively. The first pair ofrings1120A is distal to the second pair ofrings1120B. In one embodiment, the second pair of rings are disposed in the secondexpandable zone1110 and the first pair are disposed in the thirdexpandable zone1112. In another embodiment, the thirdexpandable zone1112 has an amount of overlap between adjacent rings that varies along the length of the thirdexpandable zone1112. The overlap amount can vary between each pair of adjacent rings or in a less discrete manner.FIG. 40 shows a variation in which overlap is eliminated and spacing is provided that can increase distally.
• Flexibility of thepattern1106 in the thirdexpandable zone1112 can also be varied in other ways, such as by lengthening theconnectors1128′. Because of their sinusoidal shape, the length of theconnectors1128′ can be increased (while incidentally reducing the wavelength of theconnectors1128′) without increasing the distance between the adjacent rings (e.g.,adjacent rings1120A). As illustrated inFIG. 36C, in the distal portion of the thirdexpandable zone1112, such as near the first pair ofadjacent rings1120A, the longitudinal distance between the first and second ends of theconnectors1128′ is approximately equal to the longitudinal distance between the peaks and troughs of eachcircumferential ring1120. Because of the sinusoidal shape of thesecondary connector1128′, the length of thesecondary connector1128′ is much longer than this longitudinal distance. These factors, e.g., the length of theconnector1128′, relative to the distance between adjacent rings, can provide greatly enhanced flexibility toward the distal and the thirdexpandable zone1112.
• FIG. 36D illustrates in greater detail one embodiment of thedistal portion1104. Theproximal section1104A for thedistal portion1104 includes acircumferential ring1120 and a plurality of connectors extending distally thereof. For example aconnector1128′ having a sinusoidal form can extend distally of atrough1122 of thering1120. Theconnector1128′ can include a plurality of apices, for example three apices. In one embodiment, aconnector1128′ expends distally from eachtrough1122 of thecircumferential ring1120. Aconnector1126 can extend generally circumferentially from a side surface of an arm extending between eachtrough1122 and eachcrest1124 of thering1120. Theconnector1126 enhances the stiffness ofpattern1100 in the region of opening for blood intake so that the openings will remain open when a housing incorporating thepattern1100 is expanded.
• In one embodiment thedistal section1104B of thedistal portion1104 includes acircumferential ring1132 and a plurality ofaxial members1134. Thecircumferential ring1132 may be configured to provide a larger expanded shape than the shape provided by the circumferential rings1120. For example, thecircumferential ring1132 can include a plurality ofproximal troughs1136, a plurality ofdistal crest1138, and a plurality ofelongate members1140 extending between the crests and troughs. Theelongate members1140 are substantially longer than the corresponding elongate members of the circumferential rings1120. As a result, when expanded,circumferential ring1132 provides enlarged perimeter compared to the circumferential rings1120. Theaxial members1134 can take any suitable shape, but may be configured to be integrated into an atraumatic distal structure, as discussed above. Openings are formed between adjacentaxial members1134, theelongate members1140 and thetroughs1136.
• The techniques discussed above advantageously reduce the stiffness of thewall pattern1100 at a distal location compared to a location at which an impeller will operate in a manner that spreads out deformation of the housing over a length. This isolates the impeller zone from the effect of the load L or displacement D illustrated inFIG. 35. In various embodiments, the length of the housing that is deformed is elongated to prevent focused bending that could result in a kinking of the housing, which could result in damage or significant flow blockage.
• Other techniques can be employed for modifying the location of or elongating thetransition zone1090 can be employed. For example, in one technique, the axial spacing between the circumferential rings can be varied at discrete locations or continuously along the length of the housing. The firstexpandable zone1108 can have a first axial density ofcircumferential rings1120, the secondexpandable zone1110 can have a second axial density ofcircumferential rings1120, and the thirdexpandable zone1112 can have a third axial density ofcircumferential rings1120, where at least the third density is less than the first density. Example embodiments provide a first axial density of about 8 circumferential structures per inch and a third axial density of about 4 circumferential structures per inch. In other embodiments, about one-half the axial density of circumferential structure can be provided in a more flexible zone compared to a less flexible zone. Further embodiments of enhanced flexibility due to changes in spacing of circumferential rings or structures are described below in connection withFIGS. 39 and 40.
• Varying at least one aspect of sinusoidal rings, e.g., the number of crests and troughs, the frequency of crests and/or troughs, and/or amplitude of the rings can also provide stiffness variation along the length of thepattern1100.
• One variation on the embodiment ofFIG. 36 provides for varying the pattern of thecircumferential rings1120 in different zones. For example, the firstexpandable zone1108 can havecircumferential rings1120 with a first number of distal peaks and proximal peaks and a portion of thepattern1100 distal of the firstexpandable zone1108 can havecircumferential rings1120 with a second number of distal and proximal peaks, and the first number of distal and proximal peaks can be less than the second number of distal and proximal peaks.
• In another variation, a transition zone is provided that is configured to have a continuously varying stiffness from the distal end of the firstexpandable zone1108 to theproximal section1104A of thedistal portion1104. The continuous variation of the transition zone produces an arcuate shape upon application of the load L or displacement D inFIG. 35. This advantageously eliminates or minimizes the risk of buckling or kinking of the housing into which this modified pattern is incorporated. Alternatively, a transition zone can be configured to minimize focused bending or kinking but to assure that if focused bending or kinking occurs, it will occur closer to thedistal portion1104 than to the firstexpandable zone1108.
• FIGS. 37A-37B illustrate a number of connector variations that could be incorporated into thepattern1100 to modify the stiffness between or within one of the expandable zones. In one variation, awall pattern1232 corresponding to the firstexpandable zone1108 has aconnector1128′ that has a linear configuration, for example, having only 3 apices on the connector and with a smallest amplitude compared topatterns1240 and1244, with a first plurality of (e.g., three) bends or apices that provides a first longitudinal stiffness. Awall pattern1240 corresponding to a portion of thepattern1100 that is more flexible than the firstexpandable zone1108 has aconnector1128′ that has a linear configuration with a second plurality of (e.g., five) apices and each with a larger amplitude than thepattern1232, that provides a second longitudinal stiffness. The second plurality of apices includes more bends than the first plurality. Awall pattern1244 corresponding to a portion of thepattern1100 that is more flexible than the firstexpandable zone1108 has aconnector1128′ that is much longer (i.e., having a larger amplitude or connecting material between apices) than the connectors in thepatterns1232,1240 and as a result comprises a third longitudinal stiffness that is less than the first or second longitudinal stiffnesses. Theconnector1128′ of thewall pattern1244 is much longer by spanning the entire width of a trough a plurality of times between tends connected to axially aligned troughs ofadjacent rings1120.
• FIG. 37B shows further variants in which other variable are modified. For example, awall pattern1248 is provided in which the radius of curvature of an apex toward the proximal end of aconnector1128′ is increased compared to the curvature of other apices. In other words, one segment of the connector is curved rather than straight. This arrangement can be used in a portion of a wall structure where greater stiffness is needed, such as near themembers1118 connect the proximal most circumferential ring to theproximal portion1120.
• Awall pattern1252 can include aconnector1128 with a greater number of apices, e.g., five apices compared to three inpattern1248, with comparable amounts of overlap.
• Awall pattern1256 can provide both a larger number of apices and a lesser amount of nesting or overlap betweenadjacent rings1120. Thepattern1256 includes seven apices. The apices have progressively larger amplitude to maximize the length of theconnector1128′ for a given trough to trough spacing.
• Awall pattern1260 provides another means for varying the stiffness of the structure. In thepattern1260, a similar number of apices is provided compared to thepattern1256, however, the average amplitude is less. In this embodiment, gaps G are provided in the unexpanded state between theconnector1128′ and the arms of thering1120. Thus, the length of theconnector1128′ is less than it could be given the arrangement of therings1120. By reducing the average amplitude, the overall stiffness can be enhanced other variable being held constant.
• Wall pattern1264 provides another variation similar topattern1260 except that the average amplitude is maximized by eliminating the gap G and a greater amount of nesting or overlap is provided. The resulting structure may have comparable stiffness to that ofwall pattern1264 but provide more material coverage which reduces the surface area that needs to be coated. Also, this arrangement may reduce the percentage contribution of the coating to the mechanical performance of a housing into which it is incorporated.
• Although the foregoing discussion ofFIGS. 35-37B has focused on varying thepattern1100 to control the stiffness of a housing into which it is integrated, a difference in stiffness can also be provided by changing properties of a coating disposed over thepattern1100. The coating is provided to enclose a space in a housing formed with thepattern1100 such that blood can flow therethrough. In some embodiments, the coating can be made with varying thickness to change the stiffness of the housing at a location where less stiffness is preferred. For example, the firstexpandable zone1108 can be coated with a first thickness and the secondexpandable zone1110 can be coated with a second thickness that is less than the first thickness. In other variations, the thirdexpandable zone1112 can be coated with a third thickness that is less than the first and second thicknesses. In other embodiments, a continuous and not varying mesh structure is provided and at least the second thickness of the coated material is less than the first thickness of the coated material.
• Other techniques can be applied for coating themesh203 orpattern1100 with a continuous thickness of coating but with a varying stiffness. For example, different materials could be used to coat the firstexpandable zone1108 and at least one of the second and thirdexpandable zones1110,1112. Also, the porosity of the coating can be varied along the length of the housing to change the flexibility. The porosity of the firstexpandable zone1108 can be less than that of a portion of the housing distal the firstexpandable zone1108. In one embodiment, the porosity of the firstexpandable zone1108 is less than that of the second and thirdexpandable zones1110,1112.
• FIG. 38 shows another embodiment of awall pattern1290 that provides enhanced stiffness. Is it desirable to enhance the stiffness of the firstexpandable zone1108 particularly adjacent to theproximal portion1102. This is in part because the connection between theexpandable zone1108 and the non-expanding proximal portion can be an area of focused bending. One technique for reducing the bending at this area is to provideconnectors1126A that are wider theconnectors1126.
• As discussed above, theconnectors1126 have a width that is similar to the length thereof. In this context, the length is considered the distance that the connector spans between adjacent arms of axially overlapping neighboringrings1120 and the width is a distance perpendicular to the length. In contrast, theconnectors1126A are much wider and/or longer than theconnectors1126, and are similar to theconnectors1126 while acting as a merged section along the length or a portion of the length between the adjacent arms of the nested circumferential rings. Theconnectors1126A have a width that is several times the length thereof. In one embodiment the width of theconnector1126A is at least about two times the length of theconnector1126A. In another embodiment, the width of theconnector1126A is at least about four times the length of theconnector1126A. In one embodiment, theconnector1126A is configured to extend from acrest1122 of a firstcircumferential ring1120 to atrough1124 of a secondcircumferential ring1120 that is immediately distal the first circumferential ring. In one embodiment, theconnector1126A has afirst radius portion1294 that extends from acrest1122 of the first circumferential ring to a location on an arm of the second circumferential ring that is distal of thecrest1122. Theconnector1126A also can have a second radius portion1298 that extends from atrough1124 of the second circumferential ring to a location on an arm of the first circumferential ring that is proximal of thetrough1124 of the first circumferential ring.
• In the embodiments ofFIGS. 39 and 40, changing overlap between neighboring crests and troughs is a primary technique for modifying the stiffness of a portion of awall pattern1300. Thepattern1300 can be incorporated into thehousing202. Thepattern1300 includes a relatively stiffproximal zone1304, atransition zone1308, and adistal zone1312. Other aspects of the pattern can be similar to those described above.
• Thedistal zone1312 is configured to be progressively more flexible toward the distal end of thepattern1300. In this embodiment, the spacing or overlap between neighboringrings1320 is greatest adjacent to thetransition zone1308 and decreases toward the distal end of thedistal zone1312. In theFIG. 39 embodiment, a portion of thedistal zone1312 has no overlap betweencrests1322 of aring1320 andtroughs1324 of a neighboringring1320. Also, a gap G defined betweennearest peaks1322 andtroughs1324 increases toward the distal end of thedistal zone1312.
• In the embodiment ofFIG. 39, theaxial connectors1328 in thedistal zone1312 are straight and are longitudinally aligned with the longitudinal axis of thepattern1300. Theconnectors1328 will be stiffer than other axial connectors described herein that include sinusoidal patterns. The decreasing overlap and/or increasing gap in thedistal zone1312 compensates for the relatively stiffstraight connectors1328 to provide acceptable load dampening performance.
• FIG. 40 shows a variation of thewall pattern1100 in which the region illustrated inFIG. 36C is modified to transition from at least some overlap between neighboring crests and troughs to no overlap and then to progressively larger spacing between neighboring crests and troughs. In addition, as illustrated inFIG. 40, theconnector1128″ can include a plurality of sharp, generally linear and/or angled apices/peaks (e.g., zigzag-shaped), as opposed to the sinusoidal, wave-like connector1128′ described herein. This embodiment is similar to that ofFIG. 39 but has greater flexibility, particularly in bending.
• V. Impeller Housing Configurations Providing Flow Enhancement
• FIG. 41 illustrates anotherwall pattern1400 that advantageously enhances the flow of the blood through the housing (e.g., thehousing202,1020 or other housings described herein) in which an impeller operates.
• Thewall pattern1400 includes aproximal portion1404 that has a relatively stiff arrangement. Theproximal portion1404 corresponds to the location where an impeller operates when the wall pattern is disposed in an impeller housing. At least twoproximal rings1420 are connected by a plurality of circumferential connectors, similar to those discussed above. Adistal portion1428 of thewall pattern1400 disposed distal of theproximal portion1404 is configured to enhance flow by providing a distally expanding configuration. For example, the inner diameter or cross-sectional size of the housing in which thedistal portion1428 of thewall pattern1400 is disposed can be larger than the inner diameter or cross-sectional size of the housing corresponding to theproximal portion1404. In one embodiment, the size is progressively larger, e.g., with each ring being configured to be larger than the next proximal ring.
• Thewall pattern1400 provides a distally expanding configuration by making the crest to trough distance greater in thedistal portion1428 than in theproximal portion1404. The crest to trough can be larger toward the distal end of thedistal portion1428 than adjacent to the proximal end of thedistal portion1428. The crest to trough distance of each ring can be lengthened by increasing the length of each ring that spans between a crest and adjacent trough. Another technique for increasing the expanded size of the housing is to enlarge the crests and/or the troughs. These can be enlarged by increasing an inner radius of the crest and/or trough.
• Thewall pattern1400 and associated housing is advantageous in that a heart pump operates more effectively when the inner wall of the housing directs the blood flow to the impeller. In one technique significant pump efficiency increase can be obtained by configuring thewall pattern1400 to expand in thedistal portion1428 to a diameter that is approximately 50% or more larger than in theproximal portion1404. By both maximizing the diameter at thedistal portion1428, cavitation can be reduced and flow efficiency is increased. In addition to enlarging the inner size (e.g., diameter) of location of a housing corresponding thedistal portion1428, the length of thedistal portion1428 or a portion of the housing distal the impeller can be increased. In some embodiments, a housing incorporating thewall pattern1400 can be both elongated and configured to have a distally expanding configuration to increase pump efficiency.
• In addition to use as an LVAD, the device of the present invention may also be used as a right ventricular assist device in a manner similar to that described above. Other applications of the device according to the present invention include providing additional blood flow to other organs, assisting the heart during operations and the like.
• Applications of the improved fluid pump design described herein are not limited to ventricular assist devices. The improved cannula and impeller designs are useful for any application where a stored configuration having a reduced diameter is useful for locating the pump at a desired location. For example, a fluid pump operating underground may be introduced into a pipe, channel or cavity through an opening of lesser diameter, and operate at a diameter greater than that of the opening used. Applications of an impeller deploying within an expandable cannula include a collapsible fire hose with an integral booster pump, a collapsible propeller, a biomedical pump for a biological fluid, and the like.
• VI. Methods
• As discussed above, in various embodiments theheart pump10 is inserted in a less invasive manner, e.g., using techniques that can be employed in a catheter lab. Various general techniques pertinent to theheart pump10 are described in U.S. patent application Ser. No. 12/829,359, filed on Jul. 1, 2010, and entitledBlood Pump With Expandable Cannula, which is incorporated by reference herein in its entirety and for all purposes.
• Although the inventions herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present inventions. It is therefore to be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present inventions as defined by the appended claims. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents.

Claims (51)

1. A catheter assembly for a heart pump, comprising:

an elongate tubular member;

a hub coupled with a proximal end of the elongate tubular member;

a plurality of structural members forming a distal portion of an impeller housing;

a locking device disposed between the structural members and the hub configured to prevent the elongate tubular member from being separated from the structural members when the catheter assembly is in use.

2. The catheter assembly ofclaim 1, wherein the locking device comprises a barb at the distal end of the structural members and a narrow aperture channel formed at a proximal aspect of the hub, the narrow aperture channel permitting insertion of the barb and resisting retraction of the barb.

3. The catheter assembly ofclaim 1, wherein the hub comprises a recess formed at a proximal end thereof and further comprising a core member configured to be inserted into the recess, the catheter assembly being configured to prevent the structural members from being retracted from the core member.

4. The catheter assembly ofclaim 3, wherein the structural member and the core member comprises a T-shaped configuration such that a proximal narrow portion of the recess abuts and opposes retraction of a wider portion of the structural member disposed distal thereof.

5. The catheter assembly ofclaim 3, wherein the hub is coupled to the elongate tubular member through the core member.

6. The catheter assembly ofclaim 3, wherein the core member comprises a distal portion configured to securely couple with the elongate tubular member.

7. The catheter assembly ofclaim 6, wherein the distal portion of the core member extends distally of the hub.

8. The catheter assembly ofclaim 1, wherein the hub has an increasing outer profile along its length.

9. The catheter assembly ofclaim 1, wherein the hub has an elongated tapered section having a distal end disposed distally of the distal portion of the core member to provide a dilating structure.

10. The catheter assembly ofclaim 1, wherein the hub comprises a distal portion configured to securely couple with the elongate tubular member.

11. The catheter assembly ofclaim 3, wherein a barrier structure is provided within the recess of the hub to separate at least a portion of the recess from a lumen within the catheter assembly.

12. The catheter assembly ofclaim 1, wherein the locking device comprises a through-hole in the structural members configured to permit a first portion of material disposed on an inside surface of the structural member to branch through to a second portion of material disposed on an outside surface of the structural member.

13. The catheter assembly ofclaim 12, wherein the locking device comprises a plurality of through-holes disposed along a distal length of at least one of the structural members.

14. The catheter assembly ofclaim 12, wherein the locking device comprises a circular structure disposed at the distal end of the at least one of the structural members.

15. A catheter assembly for a heart pump, comprising:

an elongate tubular member;

an expandable housing disposed at the distal end of the elongate tubular member, the expandable housing configured to house an impeller and to convey blood from an intake toward the impeller in use;

an expandable tip coupled with the distal end of the expandable housing, the expandable tip having a collapsed configuration in which a tapered profile is provided for facilitating advancement through an anatomical structure and having an expanded configuration for spacing the intake from the anatomy adjacent to where the pump is operates.

16. The catheter assembly ofclaim 15, further comprising a plurality of elongate arcuate structural members disposed between the expandable housing and the expandable tip, the arcuate structural members providing wide openings for blood intake into the housing.

17. The catheter assembly ofclaim 15, further comprising a sheath adapted to be advanced relative to the elongate tubular member to be positioned over the expandable housing and the expandable tip to maintain the tip in the collapsed configuration.

18. The catheter assembly ofclaim 17, wherein the tip comprises a plurality of arms having proximal portions configured with reduced thickness to engage with a sheath.

19. The catheter assembly ofclaim 17, wherein the tip comprises a plurality of arms coupled as their distal ends with a hub disposed around a guidewire port, the arms having proximal ends coupled with the expandable housing.

20. The catheter assembly ofclaim 15, wherein the expandable tip is bulbuous when in the expanded configuration.

21. A catheter assembly for a heart pump, comprising:

an impeller shaft and an impeller blade extending from the impeller shaft;

a housing in which the impeller shaft is journaled for rotation, the housing having an elongate wall structure disposed circumferentially about the impeller blade and extending distally and proximally thereof, a distal region of the wall structure being configured to isolate a proximal region of the wall structure from deflection due to application of loads by the heart during operation of the impeller assembly within the patient.

22. The catheter assembly ofclaim 21, wherein the wall structure comprises a first region disposed over the impeller and a second region distal the first region, the second region having less stiffness than the first region such that loads applied within or distal of the second region produces deformation of the housing that is primarily distal of the first region.

23. The catheter assembly ofclaim 22, wherein the wall structure comprises a mesh structure and a coating disposed over the mesh, the mesh structure being arranged with a first stiffness in the first region and a second stiffness in the second region, the second stiffness being less than the first stiffness.

24. The catheter assembly ofclaim 23, wherein the mesh structure in the second region has progressively less stiffness toward the distal end of the housing.

25. The catheter assembly ofclaim 23, wherein the mesh structure further comprises a third region having a third stiffness that is less than the second stiffness.

26. A percutaneous heart pump, comprising:

a catheter assembly having a proximal end, a distal end, and an elongate body disposed therebetween, the elongate body configured such that the distal end can be disposed inside heart chamber of a human patient while a proximal end is disposed outside the patient,

the distal end comprising an expandable housing being configured to be insertable into a peripheral vessel in a low profile configuration and to be expanded to a larger profile within the patient;

an impeller shaft and an impeller blade extending from the impeller shaft, the impeller shaft is journaled for rotation in the distal portion of the catheter assembly;

wherein the expandable housing comprising:

an elongate wall structure disposed circumferentially about the impeller blade and extending distally and proximally thereof, the wall being configured to maintain a gap between the blade an inner surface of the wall structure within a selected range over a range of transverse loading corresponding to forces generated during systole and diastole of the heart.

27. The percutaneous heart pump ofclaim 26, wherein the elongate wall structure comprises a metallic mesh disposed in a fluid-tight structure, the elongate wall structure having a stiffness profile that is greatest at a longitudinal position corresponding to that of the impeller blades and being decreased distally thereof.

28. The percutaneous heart pump ofclaim 27, wherein the metallic mesh structure is more dense in a region corresponding to the impeller blade and is less dense distally thereof.

29. The percutaneous heart pump ofclaim 28, wherein the metallic mesh structure comprises circumferential rings having a greater concentration in the region corresponding to the impeller blade and is less dense distally thereof.

30. The percutaneous heart pump ofclaim 28, wherein the metallic mesh structure comprises circumferential rings connected by axial connectors, the axial connectors being stiffer in the region corresponding to the impeller blade and being less stiff distally thereof.

31. The percutaneous heart pump ofclaim 27, wherein the fluid-tight structure comprises a polymeric coating, the polymeric coating being thicker in a region corresponding to the impeller blade and is less dense distally thereof.

32. A catheter assembly for a heart pump, comprising:

an impeller shaft and an impeller blade extending from the impeller shaft;

an impeller housing in which the impeller shaft is journaled for rotation, the housing comprising:

an inlet;

an outlet; and

an elongate wall structure disposed circumferentially about the impeller blade and extending distally and proximally thereof between the inlet and outlet, the wall structure adjacent to at least one of the inlet and the outlet being configured to maintain a bulbous shape when deployed.

33. The catheter assembly ofclaim 32, wherein the elongate wall structure comprises a mesh structure and a coating disposed over the mesh structure, the coating having a stiffened region adjacent the inlet to maintain a first transverse size, the transverse size of the wall structure decreasing proximally and distally of the stiffened region.

34. The catheter assembly ofclaim 33, wherein the stiffened region comprises an annular band of the wall structure that is thicker than the thickness of the wall structure proximal of the stiffened region.

35. The catheter assembly ofclaim 32, wherein the elongate wall structure comprises a mesh structure and a coating disposed over the mesh structure, the coating having a stiffened region adjacent the outlet to maintain a first transverse size and the wall structure being configured distal of the outlet to have a transverse size that is less than the first transverse size.

36. The catheter assembly ofclaim 32, wherein the impeller comprises a diffuser and the wall structure comprises a reinforced annular portion, a flared section extending distally of the annular portion and being disposed over a distal portion of the diffuser and a plurality of leaflets disposed proximally of the annular portion.

37. A catheter assembly for a heart pump, comprising:

an impeller shaft and an impeller blade extending from the impeller shaft;

a housing in which the impeller shaft is journaled for rotation, the housing having an elongate wall structure disposed circumferentially about the impeller blade and extending distally and proximally thereof, the wall structure being sufficiently deformable to be displaced by ambient conditions during operation of the impeller assembly within a patient.

38. The catheter assembly ofclaim 37, wherein the housing is sufficiently flexible to be deflected by fluid flow generated by the impeller blade upon movement of the impeller blade toward the wall.

39. The catheter assembly ofclaim 38, wherein the wall comprises a plurality of struts and a covering disposed over the struts, the struts and covering being disposed circumferentially about the impeller blade.

40. The catheter assembly ofclaim 39, wherein the plurality of struts comprises a first strut density at an axial position corresponding to the impeller blade and a second strut density greater than the first strut density at a location proximal or distal of the location of the first density.

41. The catheter assembly ofclaim 39, wherein the plurality of struts comprises a first average strut thickness at an axial position corresponding to the impeller blade and a second average strut thickness greater than the first average strut thickness at a location proximal or distal of the location of the first density.

42. The catheter assembly ofclaim 39, wherein the covering comprises a first average thickness at an axial position corresponding to the impeller blade and a second average thickness greater than the first average thickness at a location proximal or distal of the location of the first density.

43. The catheter assembly ofclaim 39, wherein the plurality of struts comprises a plurality of circumferentially extending sinusoidal member.

44. The catheter assembly ofclaim 39, wherein the sinusoidal members are elastically deformable at least along a length extending substantially from a proximal end of the impeller blade to a distal end of the impeller blade.

45. The catheter ofclaim 37, wherein the housing is sufficiently flexible to be deflected to a converging or diverging configuration at an axial position upstream of an impeller inlet plane.

46. The catheter ofclaim 37, wherein the housing is sufficiently flexible to be deflected to a diverging configuration to produce a diffusing or deswirling effect at an axial position downstream of an impeller outlet plane.

47. An impeller assembly for a heart pump, comprising:

an impeller shaft and an impeller blade extending from the impeller shaft; and

a housing in which the impeller shaft is journaled for rotation, the housing comprising an impeller blade zone, an inlet zone, and an outlet zone, the impeller blade zone being elongate and having a substantially constant transverse size at least from proximal of the impeller blade to distal of the impeller blade;

wherein the impeller zone is disposed between the inlet zone and the outlet zone; and

wherein at least one of the inlet zone and the outlet zone is configured to reduce fluttering of the housing when the heart pump is operating.

48. The impeller assembly ofclaim 47, wherein the inlet zone comprises enhanced stiffness compared to the stiffness of the impeller zone.

49. The impeller assembly ofclaim 47, wherein the outlet zone comprises enhanced stiffness compared to the stiffness of the impeller zone.

50. A catheter assembly for a heart pump, comprising:

an impeller shaft and an impeller blade extending from the impeller shaft;

a housing in which the impeller shaft is journaled for rotation, the housing having an elongate wall structure a portion of which is disposed circumferentially about the impeller blade and the impeller shaft, the wall structure being configured to provide a first stiffness over the impeller blade and a second stiffness greater than the first stiffness at a location proximal of the impeller blade to reduce bending of the housing proximal of the blade.

51. The catheter assembly ofclaim 50, wherein the wall structure comprises a first plurality of circumferential sinusoidal rings being joined by a first plurality of generally circumferentially oriented connectors to provide the first stiffness and in the and a second plurality of circumferential sinusoidal rings being joined by a second plurality of generally circumferentially oriented connectors to provide the second stiffness.

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